                 FOR PUBLICATION

  UNITED STATES COURT OF APPEALS
       FOR THE NINTH CIRCUIT


PLANNED PARENTHOOD ARIZONA,                No. 14-15624
INC.; WILLIAM RICHARDSON, M.D.,
DBA Tucson Women’s Center;                    D.C. No.
WILLIAM H. RICHARDSON, M.D.,               4:14-cv-01910-
P.C., DBA Tucson Women’s Center,                DCB
               Plaintiffs-Appellants,

                 v.                          OPINION

WILLIAM HUMBLE, Director of the
Arizona Department of Health
Services, in his official capacity,
                  Defendant-Appellee.


      Appeal from the United States District Court
               for the District of Arizona
       David C. Bury, District Judge, Presiding

                Argued and Submitted
       May 13, 2014—San Francisco, California

                      Filed June 3, 2014

     Before: Susan P. Graber, William A. Fletcher,
         and Richard A. Paez, Circuit Judges.

             Opinion by Judge W. Fletcher
2       PLANNED PARENTHOOD ARIZONA V. HUMBLE

                           SUMMARY*


                            Civil Rights

    The panel reversed the district court’s denial of plaintiff’s
motion for a preliminary injunction and remanded with
instructions that the district court issue the requested
injunction in an action seeking to enjoin enforcement of an
Arizona statute, Ariz. Rev. Stat. § 36-449.03(E)(6), and its
implementing regulation, Ariz. Admin. Code § R9-10-
1508(G), which restrict the manner in which certain
medications may be used to perform abortions.

    The panel assumed without deciding that the Arizona law,
which restricts the use of an off-label evidence-based regime
of medication abortions, passed rational basis review and
moved directly to the application of the undue burden test.
The panel held that plaintiffs introduced uncontroverted
evidence that the Arizona law substantially burdened
women’s access to abortion services, and Arizona introduced
no evidence that the law advanced in any way Arizona’s
interest in women’s health. The panel concluded that on the
record before it, the burden imposed by the Arizona law was
undue within the meaning of Planned Parenthood of Se.
Penn. v. Casey, 505 U.S. 833, 876 (1992), and Gonzales v.
Carhart, 550 U.S. 124 (2007). The panel therefore held that
the district court abused its discretion when it held that
plaintiffs were unlikely to succeed on the merits of their
undue burden claim.


  *
    This summary constitutes no part of the opinion of the court. It has
been prepared by court staff for the convenience of the reader.
       PLANNED PARENTHOOD ARIZONA V. HUMBLE               3

                       COUNSEL

Alice J. Clapman (argued), Helene T. Krasnoff, Planned
Parenthood Federation of America, Washington, D.C.;
Lawrence J. Rosenfeld, Squire Sanders LLP, Phoenix,
Arizona, for Plaintiffs-Appellants.

Robert Lawrence Ellman (argued), Solicitor General, G.
Michael Tryon, Senior Litigation Counsel, and Thomas C.
Horne, Attorney General, Arizona Attorney General’s Office,
Phoenix, Arizona, for Defendant-Appellee.

Kimberly A. Parker, Wilmer Cutler Pickering Hale and Dorr
LLP, Washington, D.C., for Amici Curiae American College
of Obstetricians and Gynecologists and the American
Medical Association.

Denise Mary Burke, Americans United for Life, Washington,
D.C., for Amici Curiae Arizona Legislators.


                        OPINION

W. FLETCHER, Circuit Judge:

    Plaintiffs Planned Parenthood Arizona, Inc., Dr. William
Richardson, and Tucson Women’s Center appeal the district
court’s denial of their motion for a preliminary injunction.
Plaintiffs seek to enjoin enforcement of an Arizona statute,
Ariz. Rev. Stat. § 36-449.03(E)(6), and its implementing
regulation, Ariz. Admin. Code § R9-10-1508(G), which
restrict the manner in which certain medications may be used
to perform abortions. The district court denied the
4      PLANNED PARENTHOOD ARIZONA V. HUMBLE

preliminary injunction because it found that plaintiffs had not
shown a likelihood of success on the merits. We reverse.

                        I. Background

    “Before 2000, most first-trimester abortions were
surgical, performed by a procedure commonly known as
vacuum aspiration or suction curettage.”         Planned
Parenthood Sw. Ohio Region v. DeWine, 696 F.3d 490, 494
(6th Cir. 2012). In 2000, the Federal Drug Administration
(“FDA”) first approved the use of medications to perform
abortions. Id.

             A. Medication Abortion Regimens

    The far-and-away most common method of medication
abortion employs a combination of two prescription drugs,
mifepristone (sometimes known as RU-486) and misoprostol.
Mifepristone ends pregnancy by blocking the hormone
progesterone, thereby causing the fertilized egg to detach
from the uterine wall. Misoprostol causes the uterus to
contract and expel its contents. In 2000, the FDA approved
mifepristone for use in medication abortions under the brand
name Mifeprex. The approved drug label for Mifeprex
described an “on-label” regimen requiring a woman to take
600 milligrams of mifepristone orally at a clinic, return to the
clinic two days later to take 400 micrograms of misoprostol
orally, and return again for a follow-up visit. These three
clinic visits are in addition to the visit Arizona law requires
for a woman to receive an in-person consultation with her
doctor at least twenty-four hours before an abortion. See
Ariz. Rev. Stat. § 36-2153. Clinical evidence submitted by
Mifeprex’s manufacturer established this on-label regimen to
be safe and effective through seven weeks of pregnancy, or
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                 5

49 days from the woman’s last menstrual period (“LMP”).
The FDA has approved misoprostol only for the treatment of
stomach ulcers.

    When the FDA approved mifepristone for use in
abortions, it imposed restrictions on mifepristone’s marketing
and distribution—but not on its use—under the FDA’s
“Subpart H” regulations. See 21 C.F.R. § 314.520. These
restrictions require the manufacturer to distribute
mifepristone only to doctors who sign an agreement “stating
that he or she possesses the necessary qualifications and will
adhere to the other requirements.” One Subpart H restriction
requires doctors to agree to provide each patient “a copy of
the Medication Guide and Patient Agreement” and obtain the
patient’s signature on the Patient Agreement. In the Patient
Agreement, the patient attests that she “understand[s]” the
steps involved in the on-label regimen. The patient agrees to
“follow my provider’s advice about when to take each drug.”
The Subpart H restrictions, Medication Guide, and Patient
Agreement do not require doctors to administer mifepristone
according to the on-label regimen. Cline v. Okla. Coal. for
Reprod. Justice, 313 P.3d 253, 261 n.17 (Okla. 2013) (per
curiam).

    By the time the FDA approved Mifeprex’s label, studies
already showed that a different regimen for medication
abortion was safe and effective through nine weeks of
pregnancy, or 63 days LMP (instead of 49 days LMP). This
regimen requires taking 200 milligrams (instead of 600
milligrams) of mifepristone orally at the clinic, taking 800
micrograms of misoprostol two days later at home (instead of
at the clinic) by dissolving the drug between the cheek and
gum, and then returning to the clinic for a follow-up visit.
Consistent with common terminology, we call this off-label
6      PLANNED PARENTHOOD ARIZONA V. HUMBLE

regimen the “evidence-based” regimen. Dr. Richardson
states in a sworn declaration that “virtually all abortion
providers” now use the evidence-based regimen. He further
states, “Few if any [providers] use the [on-label] method.”
The American College of Obstetricians and Gynecologists
strongly favors the evidence-based regimen over the on-label
regimen. Brief for American College of Obstetricians &
Gynecologists and the American Medical Ass’n as Amici
Curiae at 7–8. Notably, the district court found that the
evidence-based regimen is

       considered the best practices . . . by practicing
       doctors. . . . [T]here is a clear advantage to
       the current protocol because it may be used
       through the 9th week of pregnancy, not just
       through the 7th week, which is significant
       because many women do not discover their
       pregnancies until approximately 49 days,
       which is the end of [the] 7th week. . . . Also,
       risk factors from medical abortions . . . have
       been reduced or eliminated by the current
       [evidence-based] regimen; medication
       abortion now has a lower rate of ongoing
       pregnancies and fewer surgical interventions
       are necessary to complete the abortion
       procedure.

     Medication abortions now account for 41 percent of all
first-trimester abortions performed at Planned Parenthood
clinics nationwide. In 2012 in Arizona, 43 percent of all
abortions performed during the first nine weeks of pregnancy
were medication abortions.             Plaintiffs presented
uncontroverted evidence in the district court that many
women who choose medication abortion strongly prefer it
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                  7

over surgical abortion. Medication abortion is less invasive
than surgical abortion, which is a particularly important
consideration for survivors of rape or sexual abuse. Further,
some women have medical conditions that make medication
abortion significantly safer than surgical abortion. The
district court found that “medication abortion is extremely
safe and safer than the alternative surgical procedure, which
is also a very safe procedure.”

    Since the FDA approved mifepristone in 2000, there have
been eight known deaths from infection in women using
earlier off-label regimens (a fatality rate of less than 0.0005
percent). The FDA investigated these eight cases and found
no causal connection between the infections and the use of
mifepristone or misoprostol. A study conducted in 2013
surveyed the most recent six years of data and found no
infection-related deaths out of 711,556 medication abortions
performed under the current evidence-based regimen. James
Trussell et al., Reduction in Infection-Related Mortality Since
Modifications in the Regimen of Medical Abortion,
89 Contraception 193, 195 (2014).

    The on-label regimen fails to terminate the pregnancy in
about 1 percent of cases, and as many as 8 percent of women
following the on-label regimen require surgical-abortion
procedures to stop heavy bleeding caused by the medications.
The evidence-based regimen fails in about 0.5 percent of
cases, and fewer than 2 percent of women require subsequent
surgical-abortion procedures. Because of the larger dose of
mifepristone required by the on-label regimen, the drugs for
the on-label regimen cost $160 more than for the evidence-
based regimen. The on-label regimen also increases costs by
requiring an additional clinic visit. Finally, the evidence-
based regimen allows women to take misoprostol in their
8      PLANNED PARENTHOOD ARIZONA V. HUMBLE

homes, eliminating the risk that they will pass their
pregnancies, a process involving heavy bleeding and
cramping, during their trip home from the second clinic visit.

                     B. FDA Approval

     When the FDA approves a drug, it does so on the basis of
evidence of clinical trials submitted by the drug’s
manufacturer. The FDA generally does not conduct its own
trials. According to plaintiffs’ expert Dr. Lisa Rarick, who
participated as an FDA official in the approval process for
mifepristone, the FDA “does not authorize protocols for
drugs . . . . Rather, approval of [a drug] allows the drug
sponsor to advertise and promote the drug for a particular
use.” The drug’s manufacturer also submits a proposed label
for approval. The label “provides physicians with guidance
about how to use a drug in accordance with how the drug
sponsor requested and received FDA approval for its use.”
The label “does not impose binding obligations on
physicians.” The “FDA does not require a manufacturer to
update a drug’s [label] for new uses or protocols,” and there
rarely are sufficient economic incentives for the manufacturer
to do so.

    According to Dr. Rarick, the FDA “neither prohibit[s] nor
discourage[s]” off-label use of FDA-approved drugs. In fact,
“the FDA has repeatedly acknowledged that off-label use is
common and is sometimes required by good medical
practice.” In a 1982 “FDA Drug Bulletin,” the FDA stated:

          The [Federal Food, Drug, and Cosmetic]
       Act does not . . . limit the manner in which a
       physician may use an approved drug. Once a
       product has been approved for marketing, a
       PLANNED PARENTHOOD ARIZONA V. HUMBLE               9

       physician may prescribe it for uses or in
       treatment regimens or patient populations that
       are not included in approved labeling. Such
       “unapproved” or, more precisely, “unlabeled”
       uses may be appropriate and rational in
       certain circumstances, and may, in fact, reflect
       approaches to drug therapy that have been
       extensively reported in medical literature.

           . . . Valid new uses for drugs already on
       the market are often . . . confirmed by well-
       planned and executed clinical investigations.
       Before such advances can be added to
       the approved labeling, however, data
       substantiating the effectiveness of a new use
       or regimen must be submitted by the
       manufacturer to [the] FDA for evaluation.
       This may take time and, without the initiative
       of the drug manufacturer whose product is
       involved, may never occur. For that reason,
       accepted medical practice often includes drug
       use that is not reflected in approved drug
       labeling.

12 FDA Drug Bulletin 5 (1982). The FDA has consistently
maintained that position. See U.S. Food & Drug Admin.,
“Off-Label” and Investigational Use of Marketed Drugs,
Biologics, and Medical Devices - Information Sheet (Aug. 10,
2011), http://www.fda.gov/RegulatoryInformation/
Guidances/ucm126486.htm. Off-label use of drugs is
especially common in pediatrics, oncology, and gynecology
and obstetrics.
10     PLANNED PARENTHOOD ARIZONA V. HUMBLE

                  C. Arizona Legislation

   In 2012, the Arizona legislature passed House Bill 2036,
a collection of statutory amendments regulating abortion.
The amendment at issue in this case regulates medication
abortion. It provides:

       The director [of the Arizona Department of
       Health Services] shall adopt rules relating to
       the abortion procedure. At a minimum these
       rules shall require . . . [t]hat any medication,
       drug or other substance used to induce an
       abortion is administered in compliance with
       the protocol that is authorized by the United
       States [F]ood and [D]rug [A]dministration
       and that is outlined in the final printing
       labeling instructions for that medication, drug
       or substance.

Ariz. Rev. Stat. § 36-449.03(E)(6). Defendant William
Humble, Director of Arizona’s Department of Health
Services, adopted an implementing regulation as required by
the amendment. Ariz. Admin. Code § R9-10-1508(G). The
regulation had an effective date of April 1, 2014. We refer to
the amendment and regulation collectively as “the Arizona
law.”

    The legislature described its purpose in passing the
Arizona law as “[p]rotect[ing] women from the dangerous
and potentially deadly off-label use of abortion-inducing
drugs, such as, for example, mifepristone” and “[e]nsur[ing]
that physicians abide by the protocol tested [sic] and
approved by the United States Food and Drug Administration
for such abortion-inducing drugs.” The legislative findings
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                  11

describe various health risks from the use of mifepristone,
including risks of infection and hemorrhage. The district
court found that the Arizona legislature provided no
“supporting evidence for any asserted legislative fact.” The
court observed that “the risks associated with medication
abortions, relied on by the State as the reason for adopting the
[on-label] protocol, have been substantially reduced or
eliminated” by the evidence-based regimen.

              D. Challenge to the Arizona Law

    There are currently ten abortion providers in Arizona,
located in three of the state’s fifteen counties. Planned
Parenthood Arizona, Inc. (“PPAZ”), provides abortions at its
clinics in Glendale, Tempe, Tucson, and Flagstaff. PPAZ
performs medication abortions according to the evidence-
based regimen. The Glendale, Tempe, and Tucson clinics
provide both surgical and medication abortions. The
Flagstaff clinic provides only medication abortions. PPAZ’s
Flagstaff clinic is the only abortion provider in northern
Arizona. The next closest provider is in Glendale, which is
located, on average, 160 miles from locations in northern
Arizona; it is 372 miles away from some locations. In 2013,
PPAZ provided 6,667 abortions for women through 63 days
LMP. Thirty-eight percent were medication abortions.
Twenty-six percent of these medication abortions occurred
after 49 days LMP. Because they occurred after 49 days
LMP, such abortions would not have been available if PPAZ
had been required to follow the on-label regimen.

   PPAZ’s Flagstaff clinic used to provide medication
abortions through an advanced practice clinician instead of a
doctor, but Arizona banned that practice in 2011. The
Flagstaff clinic could not provide abortions of any kind until
12     PLANNED PARENTHOOD ARIZONA V. HUMBLE

February 2014, when it found a doctor to perform medication
abortions. During the period when the Flagstaff clinic could
not perform abortions, significantly fewer women in northern
Arizona obtained abortions than before 2011.

    Dr. Richardson owns and operates Tucson Women’s
Center, where he provides surgical and medication abortions.
Dr. Richardson performs medication abortions according to
the evidence-based regimen. In 2013, he provided abortions
to 932 women, 660 of whom were nine weeks pregnant (63
days LMP) or less. Of those 660 women, 43 percent chose
medication abortion.

    PPAZ, Dr. Richardson, and Tucson Women’s Center sued
Director Humble in his official capacity, seeking declaratory
and injunctive relief against the Arizona law.               For
convenience, we refer to the defendant as “Arizona.”
Plaintiffs brought their claims on behalf of themselves, their
patients, and the physicians they employ. See Isaacson v.
Horne, 716 F.3d 1213, 1221 (9th Cir. 2012), cert. denied,
134 S. Ct. 905 (2014). Plaintiffs moved for a preliminary
injunction, asserting that the Arizona law is
unconstitutionally vague, violates women’s fundamental
rights to abortion and bodily integrity, and violates equal
protection. The district court denied the motion. It found that
the evidence-based regimen “is considered the best
practices,” and that Arizona had not presented any evidence
to support its legislative findings or to show that the law
actually advances women’s health. It treated these findings
as legally irrelevant. It held that the Arizona law is not vague
and does not violate equal protection or a woman’s right to
bodily integrity. It held further that the law rationally
advances Arizona’s interest in women’s health and does not
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                     13

impose an undue burden on Arizona women’s right to
abortion.

    Plaintiffs timely appealed and filed an emergency motion
for an injunction pending appeal. A motions panel of this
court enjoined enforcement of the Arizona law pending
appeal and expedited the appeal. See Planned Parenthood of
Ariz., Inc. v. Humble, No. 14-15624 (9th Cir. Apr. 8, 2014)
(order granting emergency injunction).

                         II. Discussion

           A. Standard for Preliminary Injunctions

    We review the district court’s denial of a preliminary
injunction for abuse of discretion. Alliance for the Wild
Rockies v. Cottrell, 632 F.3d 1127, 1131 (9th Cir. 2011).
Reliance “on an erroneous legal standard” is an abuse of
discretion. Id. (internal quotation marks omitted). We
review the district court’s legal conclusions de novo and its
factual findings for clear error. Id.

    “A plaintiff seeking a preliminary injunction must
establish that he is likely to succeed on the merits, that he is
likely to suffer irreparable harm in the absence of preliminary
relief, that the balance of equities tips in his favor, and that an
injunction is in the public interest.” Winter v. Natural Res.
Def. Council, Inc., 555 U.S. 7, 20 (2008). “‘[S]erious
questions going to the merits’ and a balance of hardships that
tips sharply towards the plaintiff can support issuance of a
preliminary injunction, so long as the plaintiff also shows that
there is a likelihood of irreparable injury and that the
injunction is in the public interest.” Alliance for the Wild
Rockies, 632 F.3d at 1135.              “[T]he deprivation of
14     PLANNED PARENTHOOD ARIZONA V. HUMBLE

constitutional rights ‘unquestionably constitutes irreparable
injury.’” Melendres v. Arpaio, 695 F.3d 990, 1002 (9th Cir.
2012) (quoting Elrod v. Burns, 427 U.S. 347, 373 (1976)).

                  B. Success on the Merits

            1. Interpretation of the Arizona Law

    The parties disagree about the correct interpretation of the
Arizona law. Plaintiffs argue that, under a proper reading of
its text, the law flatly prohibits all medication abortions.
Arizona disagrees. It argues that the law allows medication
abortions, but only if they are performed in accordance with
the on-label regimen. We need not resolve this dispute. We
assume for the purposes of our analysis that Arizona’s
interpretation of the law is correct.

                      2. Undue Burden

    Plaintiffs argue that the Arizona law is unconstitutional
because it imposes an undue burden on a woman’s right to
abortion. See Planned Parenthood of Se. Penn. v. Casey,
505 U.S. 833, 876 (1992). In Casey, a plurality of the
Supreme Court rejected both strict scrutiny and rational-basis
review of abortion regulations, holding instead that laws
regulating pre-viability abortions are unconstitutional if they
impose an “undue burden” on a woman’s right to abortion.
Id. at 876. Casey recognized that states have legitimate
“interests in maternal health and protecting fetal life [that]
can, in some circumstances, justify regulations of abortion.”
Tucson Woman’s Clinic v. Eden, 379 F.3d 531, 539 (9th Cir.
2004). The undue burden test seeks to balance those interests
with a woman’s fundamental right to abortion. See id. The
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                  15

only interest Arizona asserts in this case is its interest in
women’s health.

    Our undue burden analysis starts with Casey’s plurality
opinion. See Isaacson, 716 F.3d at 1222 n.8. The plurality
explained, “A finding of an undue burden is a shorthand for
the conclusion that a state regulation has the purpose or effect
of placing a substantial obstacle in the path of a woman
seeking an abortion of a nonviable fetus.” Casey, 505 U.S. at
877. Of the four Supreme Court cases addressing abortion
since Casey, only Gonzales v. Carhart, 550 U.S. 124 (2007),
provides meaningful guidance on how to apply Casey’s
undue burden test. Cf. Ayotte v. Planned Parenthood of N.
New England, 546 U.S. 320, 323 (2006) (addressing only the
scope of equitable relief); Stenberg v. Carhart, 530 U.S. 914,
938 (2000) (interpreting a statute in a way that the state
conceded imposed an undue burden); Mazurek v. Armstrong,
520 U.S. 969, 972 (1997) (per curiam) (addressing the
evidence required to support a finding of improper legislative
purpose). Gonzales emphasized the balance struck by Casey,
holding that a state may “regulat[e] the medical profession in
order to promote respect for life,” so long as the state does
not act irrationally or “impose an undue burden” on a
woman’s right to abortion. 550 U.S. at 158. It held that a
court reviewing an abortion regulation “must determine
whether the [regulation] furthers the legitimate interest of the
Government in protecting the life of the fetus that may
become a child.” Id. at 146.

   The analysis in both Casey and Gonzales focused on state
laws purporting to advance the state’s interest in fetal life.
Here, however, the Arizona law purports to advance
Arizona’s interest in women’s health. We wrote in Eden,
16     PLANNED PARENTHOOD ARIZONA V. HUMBLE

        [Casey’s] application of the “undue burden”
        standard is often not extendable in obvious
        ways to the context of a law purporting to
        promote maternal health.

            In the context of a law purporting to
        promote fetal life, whatever obstacles that law
        places in the way of women seeking abortions
        logically serve the interest the law purports to
        promote—fetal life—because they will
        prevent some women from obtaining
        abortions. By contrast, in the context of a law
        purporting to promote maternal health, a law
        that is poorly drafted or which is a pretext for
        anti-abortion regulation can both place
        obstacles in the way of women seeking
        abortions and fail to serve the purported
        interest very closely, or at all.

379 F.3d at 539–40 (citations omitted).

    In Eden, we described our approach to applying Casey’s
undue burden test. Under Eden, we compare the extent of the
burden a law imposes on a woman’s right to abortion with the
strength of the state’s justification for the law. See id. at 542.
The more substantial the burden, the stronger the state’s
justification for the law must be to satisfy the undue burden
test; conversely, the stronger the state’s justification, the
greater the burden may be before it becomes “undue.” On
one extreme, Eden described cases where “a purported health
regulation fails to rationally promote an interest in maternal
health on its face.” Id. at 540. In such a case, the regulation
fails even rational-basis review, and “the undue burden
standard is not triggered at all.” Id. On the other extreme,
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                   17

laws that are “harmless” or that have only an “incidental
effect” on abortion require little justification. Mazurek,
520 U.S. at 972; Casey, 505 U.S. at 874. In cases between
those two extremes, we must weigh the burdens against the
state’s justification, asking whether and to what extent the
challenged regulation actually advances the state’s interests.
If a burden significantly exceeds what is necessary to advance
the state’s interests, it is “undue.” See Webster’s Third New
Int’l Dictionary 2492 (1993) (defining “undue” as
“excessive” or “unwarranted”).

    Our approach in Eden follows from Casey, in which the
plurality wrote that “[u]nnecessary health regulations that
have the purpose or effect of presenting a substantial obstacle
to a woman seeking an abortion impose an undue burden on
the right.” 505 U.S. at 878 (emphasis added); see Eden,
379 F.3d at 542 (relying on evidence that a regulation was
“unnecessary as a matter of public health”). Whether a
regulation is necessary depends on whether and how well it
serves the state’s interest. “[T]he means chosen by the State
to further the interest in potential life must be calculated to
inform the woman’s free choice, not hinder it.” Casey,
505 U.S. at 877. The same is true for laws purporting to
protect women’s health: they “must be calculated” to advance
women’s health, “not hinder it.” Id.

    Under this approach, the plurality in Casey upheld a law
requiring, with some exceptions, minors to get consent from
their parents before obtaining an abortion. Id. at 899. The
plurality did so based on the state’s “quite reasonable
assumption that minors will benefit from consultation with
their parents and that children will often not realize that their
parents have their best interests at heart.” Id. at 895. At the
same time, a majority of the Court struck down a law
18     PLANNED PARENTHOOD ARIZONA V. HUMBLE

requiring married women to get consent from their husbands.
Id. at 887–95. The Court distinguished parental consent from
spousal consent based on the state’s comparatively weaker
justification in the second instance. While the state could
assume that minors might not realize their own best interests,
it could not “adopt a parallel assumption about adult women.”
Id. at 895.

    Similarly, the Court in Gonzales upheld the federal
Partial-Birth Abortion Ban Act of 2003 only after finding that
the Act would advance the state’s interest in fetal life by
“encourag[ing] some women to carry the[ir] infant to full
term, thus reducing the absolute number of late-term
abortions.” 550 U.S. at 160. Importantly for this case,
Gonzales held that a court applying the undue burden test
should not “place dispositive weight on [legislative] findings.
The Court retains an independent constitutional duty to
review factual findings where constitutional rights are at
stake. . . . Uncritical deference to [the legislature’s] factual
findings in these cases is inappropriate.” Id. at 165–66.

    In Planned Parenthood of Wisconsin, Inc. v. Van Hollen,
738 F.3d 786 (7th Cir. 2013), the Seventh Circuit adopted an
approach much like ours in Eden. The court affirmed a
preliminary injunction against a Wisconsin law that required
abortion providers’ doctors to have admitting privileges at a
hospital within thirty miles of the provider’s clinic. See id. at
787, 798. The state’s only justification for the law was
protection of women’s health. Id. at 789. As in Eden, the
Seventh Circuit analyzed whether the Wisconsin law actually
advanced that interest and found, on the record before it, that
the law did not. See id. at 789–91, 797–98. The court wrote,
“The cases that deal with abortion-related statutes sought to
be justified on medical grounds require not only evidence . . .
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                  19

that the medical grounds are legitimate but also that the
statute not impose an ‘undue burden’ on women seeking
abortions. The feebler the medical grounds, the likelier the
burden, even if slight, [is] to be ‘undue’ in the sense of
disproportionate or gratuitous.” Id. at 798 (citations omitted).

    The district court in this case did not cite or discuss our
decision in Eden. It relied instead on decisions of the Fifth
and Sixth Circuits. See Planned Parenthood of Greater Tex.
Surgical Health Servs. v. Abbott, No. 13-51008, 2014 WL
1257965, at *7–8 (5th Cir. Mar. 27, 2014); DeWine, 696 F.3d
at 513–18 (opinion of McKeague, J.). In applying the undue
burden test, the Fifth and Sixth Circuits consider the state’s
justification only for the very limited purpose of applying
rational-basis review. Once an abortion regulation survives
rational-basis review, these circuits pay no attention to
whether the regulation has been shown actually to advance
the state’s legitimate interests. In Abbott, the Fifth Circuit
held that courts may not consider the strength of the state’s
justification, stating that an abortion regulation need only be
supported by “rational speculation.” 2014 WL 1257965, at
*7–8 (internal quotation marks omitted). In DeWine, the
Sixth Circuit analyzed whether an Ohio abortion regulation
was an undue burden without considering the strength of the
state’s justification for the regulation. 696 F.3d at 513–18.

    We conclude that Abbott and DeWine are inconsistent
with the undue burden test as articulated and applied in Casey
and Gonzales. The Fifth and Sixth Circuits’ approach fails to
recognize that the undue burden test is context-specific, and
that both the severity of a burden and the strength of the
state’s justification can vary depending on the circumstances.
See Eden, 379 F.3d at 541 (citing Casey, 505 U.S. at 901).
We adhere to the approach in Eden and Van Hollen, which
20     PLANNED PARENTHOOD ARIZONA V. HUMBLE

requires us to weigh the extent of the burden against the
strength of the state’s justification in the context of each
individual statute or regulation.

    We assume without deciding that the Arizona law passes
rational-basis review and move directly to the application of
the undue burden test. See Eden, 379 F.3d at 540–41. In
order to show an undue burden, plaintiffs must show that, “‘in
a large fraction of the cases in which [the law] is relevant, it
will operate as a substantial obstacle to a woman’s choice to
undergo an abortion.’” Id. at 539 (quoting Casey, 505 U.S.
at 895) (alteration in Eden). We limit our inquiry to “the
group for whom the law is a restriction, not the group for
whom the law is irrelevant.” Casey, 505 U.S. at 894. Under
this limitation, we address the burden on women who, in the
absence of the Arizona law, would receive medication
abortions under the evidence-based regimen. See id. at
894–95.

    We start with the strength of Arizona’s justification for
the law. On the record before us, Arizona has presented no
evidence whatsoever that the law furthers any interest in
women’s health. The district court found that there was no
“supporting evidence for any asserted legislative fact,” and
that the evidence-based regimen has a “clear advantage” over
the on-label regimen. For example, the Arizona legislature
cited the dangerousness of mifepristone in support of
requiring the on-label regimen, but the on-label regimen
requires three times more mifepristone than the evidence-
based regimen. As the district court found, the FDA not only
expects off-label use but encourages it as part of the effective
practice of medicine. The Supreme Court itself has noted that
off-label use “is an accepted and necessary corollary of the
FDA’s mission.” Buckman Co. v. Plaintiffs’ Legal Comm.,
       PLANNED PARENTHOOD ARIZONA V. HUMBLE               21

531 U.S. 341, 350 (2001); accord id. at 350–51 & n.5.
Arizona argues that the law prohibits not just safe evidence-
based regimens for medication abortion but also other,
dangerous off-label regimens. But the record contains no
evidence that any such dangerous regimen exists or has ever
been used by any abortion provider. Therefore, on the current
record, the Arizona law appears wholly “unnecessary as a
matter of [women’s] health.” Eden, 379 F.3d at 542.

    We turn now to the burden imposed by the Arizona law.
Eden provides a nonexhaustive list of factors relevant to
whether a law imposes an undue burden. First, “[a]
significant increase in the cost of abortion or the supply of
abortion providers and clinics can, at some point, constitute
a substantial obstacle to a significant number of women.”
379 F.3d at 541. Under this factor, plaintiffs may rely on
such evidence as “testimony that one provider may be forced
to stop practicing medicine.” Id. at 542. Second, we may
consider evidence that a law “delays and deters patients
obtaining abortions, and that delay in abortion increases
health risks.” Id. Third, we may consider a law’s
“stigmatizing of abortion practice and usurping of providers’
ability to exercise medical judgment.” Id. at 543. We may
also consider the ways in which an abortion regulation
interacts with women’s lived experience, socioeconomic
factors, and other abortion regulations. See Casey, 505 U.S.
at 887–94 (relying on the effect of domestic abuse on women
seeking abortions); Van Hollen, 738 F.3d at 796 (citing the
cumulative effect of different abortion regulations);
McCormack v. Hiedeman, 694 F.3d 1004, 1016–18 (9th Cir.
2012) (describing the intersection of socioeconomic factors
and abortion regulations).
22     PLANNED PARENTHOOD ARIZONA V. HUMBLE

    Plaintiffs introduced evidence that medication abortion is
a common procedure strongly favored over surgical abortion
by many women. During the eighth and ninth weeks of
pregnancy, the Arizona law requires these women to undergo
surgical abortions rather than medication abortions. During
the first seven weeks of pregnancy, the law requires them to
undergo the on-label regimen for medication abortions. For
a significant number of women, the law will effectively ban
medication abortions outright because many women do not
discover they are pregnant before 49 days LMP, the last day
the on-label regimen is available under the law. Even for
women who discover their pregnancies earlier, practical
considerations, such as the frequency with which clinics can
see patients and the difficulties women face in obtaining time
off from work or transportation to a clinic, may effectively
preclude medication abortion before 49 days LMP.
According to the sworn declaration of Beth Otterstein, the
main clinician at PPAZ’s Flagstaff clinic, some women so
strongly prefer medication abortion, and so object to surgical
abortion, that they will forego abortion entirely if they cannot
obtain a medication abortion.

    Taking into consideration the cost of the extra dosage of
medicine and of the clinic time imposed by the required
additional visit, the on-label regimen costs at least $200 more
than the evidence-based regimen. The additional clinic visit
also increases costs to the patient for transportation, gas,
lodging, and the time she must take off from work. Plaintiffs’
evidence shows that these increased costs would reduce the
number of women who receive abortions, many of whom,
including 40 percent of PPAZ’s patients, are poor. Plaintiffs
introduced evidence from abortion providers that, for these
women, the additional costs are significant and sometimes
prohibitive. Plaintiffs introduced a sworn declaration from
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                  23

the medical director of Planned Parenthood of Greater Ohio
(“PPGO”), who declared that after Ohio limited medication
abortions to the on-label regimen, the number of medication
abortions performed by PPGO dropped by almost 65 percent.
One of PPGO’s clinics was forced to stop providing abortions
entirely.

    Plaintiffs also introduced evidence that PPAZ’s Flagstaff
clinic may have to close if it is limited to performing on-label
medication abortions. Otterstein described that as “a likely
possibility.” Plaintiffs provided specific reasons, tied to the
predicted decrease in women who would obtain medication
abortions, to explain why the Flagstaff clinic might be
compelled to close for economic reasons. Plaintiffs’ evidence
shows that the closure of the Flagstaff clinic would
significantly reduce the number of Arizona women who
receive abortions. If the Flagstaff clinic closes, women in
northern Arizona who want medication abortions will have to
make four visits to the Glendale clinic. Each visit will
require, on average, a 321-mile round trip. Some women will
have to travel up to 744 miles round-trip for each visit.
Otterstein declared that, during the period between 2011 and
2014 when PPAZ’s Flagstaff clinic could not provide
abortions, many patients said they could not travel to the
Glendale clinic and would have to forego abortions entirely.
During that period, 48 percent fewer women in northern
Arizona received medication abortions from PPAZ, and 35
percent fewer received any abortion from PPAZ, compared
with the pre-2011 period. In 2012, 31 percent fewer women
in Arizona’s three northeastern counties received any
abortion from any provider compared with 2010, when the
Flagstaff clinic was providing medication abortions.
24     PLANNED PARENTHOOD ARIZONA V. HUMBLE

    Finally, plaintiffs introduced evidence that the Arizona
law may delay abortions, thereby increasing health risks. See
Eden, 379 F.3d at 542. Dr. Daniel Grossman, a board-
certified obstetrician-gynecologist, provided a sworn
declaration in which he cited a Washington study that found
“that rural women who had to travel more than 75 miles to
obtain an abortion were two to three times more likely than
women travelling less than 75 miles to terminate after 12
weeks.” Dr. Grossman declared that “delaying abortions until
later in pregnancy drives up the risks of complications.” If
the Flagstaff clinic closes, most women in northern Arizona
will have to travel more than 75 additional miles to obtain an
abortion. Although there may be cases in which additional
travel time does not in itself rise to the level of an undue
burden, this factor must be evaluated on a case-by-case basis
and balanced against the strength of the state’s interest.
Casey, 505 U.S. at 885–86.

    Plaintiffs have introduced uncontroverted evidence that
the Arizona law substantially burdens women’s access to
abortion services, and Arizona has introduced no evidence
that the law advances in any way its interest in women’s
health. Plaintiffs’ evidence shows that the Arizona law
“usurp[s] . . . providers’ ability to exercise medical
judgment,” Eden, 379 F.3d at 543, by requiring them to
administer a less safe, less effective treatment regimen. See
Brief for American College of Obstetricians & Gynecologists
and the American Medical Ass’n as Amici Curiae at 13–17.
The district court found that “medication abortion is
extremely safe and safer than the alternative surgical
procedure.” It also found that the evidence-based regimen is
safer and more effective than the on-label regimen. On the
record before us, we conclude that the burden imposed by the
Arizona law is undue within the meaning of Casey and
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                  25

Gonzales. See Casey, 505 U.S. at 877; Gonzales, 550 U.S. at
146, 158. We therefore hold that the district court abused its
discretion when it held that plaintiffs were unlikely to
succeed on the merits of their undue burden claim.

    On the current record, the burden imposed by the Arizona
law is undue even if some women who are denied a
medication abortion under the evidence-based regimen will
nonetheless obtain an abortion. Neither the Supreme Court
nor this court has ever held that a burden must be absolute to
be undue. See Eden, 379 F.3d at 540–43 (not requiring
evidence that women would be totally prevented from
obtaining abortions). Evidence in the record shows that
women in Arizona will be burdened with a significant
increase in the cost of medication, and that many women will
be delayed in, or deterred from, seeking an abortion if the
evidence-based regimen is foreclosed to them. The
availability of on-label medication abortions during the first
seven weeks of pregnancy, and of surgical abortions
thereafter, therefore does not preclude a finding of undue
burden.

    The Court in Gonzales upheld the federal ban on late-term
dilation and extraction abortion (“D&X”), citing the
availability of a safe alternative late-term procedure, dilation
and evacuation abortion (“D&E”). 550 U.S. at 166–67. But
Gonzales did not hold that the existence of a safe alternative
procedure is, in itself, determinative. The undue burden
claim in Gonzales was based only on the law’s failure to
allow D&X when required to protect a woman’s health. Id.
at 161–67. Gonzales did not address the relevance of safe
alternative procedures in challenges based on other kinds of
burden. And in Gonzales, the challenged law left in place “a
commonly used and generally accepted method” that was
26     PLANNED PARENTHOOD ARIZONA V. HUMBLE

very similar to the one it banned. Id. at 165. Therefore, the
burden in Gonzales was slight, while the government’s
interest in fetal life was sufficient to justify the burden. Here,
the Arizona law imposes a greater burden and is not justified
by any interest. Moreover, for women between 49 and 63
days LMP, the Arizona law prohibits medication abortion
entirely, leaving surgical abortion as the only legal
alternative. In contrast to D&E and D&X, medication
abortion and surgical abortion are very dissimilar procedures.

    The court in Van Hollen granted a preliminary injunction
against the enforcement of the Wisconsin law on the ground
that “the medical grounds thus far presented . . . are feeble,
yet the burden great.” 738 F.3d at 798. Here, the “medical
grounds thus far presented” are not merely “feeble.” They
are non-existent. On the current record, the Arizona law
imposes an undue—and therefore unconstitutional—burden
on women’s access to abortion. We therefore conclude, at
this stage of the proceedings, that plaintiffs have shown that
they are likely ultimately to succeed on the merits of their
undue burden claim.

    In its brief to us, Arizona does not argue that plaintiffs
have not shown a likelihood of irreparable harm or that the
balance of hardships and the public interest do not favor a
preliminary injunction. See Alliance for the Wild Rockies,
632 F.3d at 1135. Therefore, any argument based on these
factors is waived. See Thompson v. Runnels, 705 F.3d 1089,
1103 (9th Cir. 2013). Because we hold that plaintiffs have
shown a likelihood of success on their undue burden claim,
we do not reach their other claims. We express no view on
the merits of those claims.
       PLANNED PARENTHOOD ARIZONA V. HUMBLE                 27

                         Conclusion

    We hold that plaintiffs have shown a likelihood of success
on their claim that the Arizona law imposes an undue burden
on a woman’s right to abortion. We therefore reverse the
district court’s denial of plaintiffs’ motion for a preliminary
injunction and remand with instructions to issue the requested
preliminary injunction.

   REVERSED and REMANDED.
