  United States Court of Appeals
      for the Federal Circuit
                ______________________

                 SIMPLEAIR, INC.,
                  Plaintiff-Appellant

                          v.

                   GOOGLE LLC,
                  Defendant-Appellee
                ______________________

                      2016-2738
                ______________________

   Appeal from the United States District Court for the
Eastern District of Texas in No. 2:16-cv-00488-JRG,
Judge J. Rodney Gilstrap.
                ______________________

               Decided: March 12, 2018
               ______________________

    JOHN JEFFREY EICHMANN, Dovel & Luner, LLP, Santa
Monica, CA, argued for plaintiff-appellant. Also repre-
sented by GREGORY S. DOVEL, SIMON FRANZINI.

    CHARLES KRAMER VERHOEVEN, Quinn Emanuel Ur-
quhart & Sullivan, LLP, San Francisco, CA, argued for
defendant-appellee.   Also represented by CARL G.
ANDERSON, JORDAN ROSS JAFFE; MILES DAVENPORT
FREEMAN, Los Angeles, CA.
                ______________________

    Before LOURIE, REYNA, and CHEN, Circuit Judges.
2                             SIMPLEAIR, INC.   v. GOOGLE LLC



LOURIE, Circuit Judge.
     SimpleAir, Inc. (“SimpleAir”) appeals from the order
of the United States District Court for the Eastern Dis-
trict of Texas dismissing SimpleAir’s complaint under
Rule 12(b)(6) as barred by claim preclusion and the Kess-
ler doctrine. SimpleAir, Inc. v. Google Inc., 204 F. Supp.
3d 908, 915 (E.D. Tex. 2016) (“SimpleAir IV”). Because
the district court erred by presuming that terminally-
disclaimed continuation patents are patentably indistinct
variations of their parent patents without analyzing the
scope of the patent claims, we vacate the district court’s
order and remand for further proceedings consistent with
this opinion.
                      BACKGROUND
    SimpleAir initiated a series of patent infringement
lawsuits over six years ago against Google’s Cloud Mes-
saging and Cloud to Device Messaging Services (collec-
tively, “GCM”). Thus far, the litigation has resulted in
three judgments of noninfringement in Google’s favor.
Each case has involved one or more patents from a family
of patents owned by SimpleAir directed to push notifica-
tion technology. The question in this case is whether
claim preclusion or the Kessler doctrine bars SimpleAir’s
fourth suit asserting additional terminally-disclaimed
continuation patents from this family against Google and
its GCM services.
    The parent patent of this family is U.S. Patent
6,021,433 (the “’433 patent”), which was filed January 24,
1997, claimed priority from a provisional application filed
January 26, 1996, issued February 1, 2000, and expired
January 24, 2017. The rest of SimpleAir’s patents assert-
ed against GCM are children of the ’433 patent linked by
continuation applications (collectively, the “child pa-
tents”). The child patents all share a common specifica-
tion with the ’433 patent and also claim priority from the
1996 provisional application. During prosecution, Sim-
SIMPLEAIR, INC.   v. GOOGLE LLC                           3



pleAir filed terminal disclaimers for each child patent to
overcome obviousness-type double patenting rejections at
the U.S. Patent and Trademark Office (“PTO”). The
terminal disclaimers require the child patents to expire
on the same day as the ’433 patent, see 35 U.S.C. § 253(b),
and also require the child patents to be “commonly owned
with the application or patent which formed the basis” for
the obviousness-type double patenting rejection, see 37
C.F.R. § 1.321(c)(3). The child patents issued over the
course of eight years between 2006 and 2014.
     SimpleAir filed its first lawsuit against Google in
2011, asserting the ’433 patent and a continuation, U.S.
Patent 7,035,914 (the “’914 patent”). SimpleAir dismissed
its action based on the ’433 patent with prejudice, but the
parties proceeded to trial on the ’914 patent. A jury found
the ’914 patent not invalid and infringed by Google’s GCM
services, see SimpleAir, Inc. v. Google Inc., 70 F. Supp. 3d
747, 752 (E.D. Tex. 2014), but on appeal we reversed the
district court’s claim construction ruling, vacated the jury
verdict, and remanded with instructions to enter judg-
ment of noninfringement, SimpleAir Inc. v. Sony Ericsson
Mobile Commc’ns AB, 820 F.3d 419, 421 (Fed. Cir. 2016)
(“SimpleAir I”).
    While SimpleAir I was proceeding, SimpleAir filed
two more complaints asserting that GCM infringed two
other continuations, U.S. Patents 8,572,279 (the “’279
patent”) and 8,601,154 (the “’154 patent”). The district
court consolidated the actions, and SimpleAir dismissed
its action based on the ’154 patent with prejudice. The
parties proceeded to trial on the ’279 patent, the jury
returned a verdict of noninfringement, and the district
court entered final judgment in accordance with the
verdict, SimpleAir, Inc. v. Google Inc., No. 2:14-cv-11
(E.D. Tex. Nov. 4, 2015) (“SimpleAir II/III”).
    The present case arises from SimpleAir’s fourth com-
plaint asserting infringement by GCM, this time of U.S.
4                             SIMPLEAIR, INC.   v. GOOGLE LLC



Patents 8,639,838 (the “’838 patent”) and 8,656,048 (the
“’048 patent”). Like the ’914, ’154, and ’279 patents, the
’838 and ’048 patents are linked with the ’433 patent by
continuation applications and are terminally-disclaimed
to it.
     The district court dismissed both complaints under
Rule 12(b)(6) as barred by claim preclusion and the Kess-
ler doctrine. SimpleAir IV, 204 F. Supp. 3d at 915. The
only element of claim preclusion in dispute was whether
the present case and the previous cases involved the same
claim or cause of action. The district court held that they
did because the ’838 and ’048 patents shared the same
title and specification with the previously adjudicated
continuation patents, and the filing of a terminal dis-
claimer to overcome the PTO’s obviousness-type double
patenting rejections indicated that the PTO believed the
content of the patents in suit to be patentably indistinct
from the earlier patents. Id. at 913. That led the district
court to conclude that the underlying invention claimed
by the various child patents was the same. Id. In its
order, the district court never compared the claims of the
’838 and ’048 patents to those of the previously adjudicat-
ed patents. Id.
    Furthermore, the district court found that there was
no dispute that SimpleAir could have included the ’838
and ’048 patents in SimpleAir II/III, as the ’838 patent
issued before, and the ’048 patent issued only a few days
after, SimpleAir filed its first amended complaint in that
case. Id. at 914. By failing to amend its complaint to
include these two patents, and instead filing a new suit
just after our decision in SimpleAir I, the district court
found that SimpleAir made a “strategic decision.” Id.
    The district court also observed that the PTO’s regu-
lation requiring common ownership of terminally-
disclaimed continuation patents and their parent patents
functioned to prevent successive lawsuits brought by
SIMPLEAIR, INC.   v. GOOGLE LLC                           5



multiple assignees, id. at 913 (citing In re Hubbell, 709
F.3d 1140, 1145 (Fed. Cir. 2013)), but did not prevent
successive suits by a single patentee. The district court
reasoned that traditional claim preclusion principles
could rectify this apparent inconsistency. Id. at 914.
    Additionally, the district court held that the Kessler
doctrine barred SimpleAir’s assertion of the ’838 and ’048
patents against Google’s provision of GCM services occur-
ring after the judgment in SimpleAir II/III, although
claim preclusion did not. Id.
    SimpleAir timely appealed. We have jurisdiction un-
der 28 U.S.C. § 1295(a)(1).
                          DISCUSSION
    SimpleAir principally argues on appeal that claim
preclusion only applies when the earlier and later cases
involve the same cause of action, and “[e]ach patent
asserted raises an independent and distinct cause of
action.” Kearns v. Gen. Motors Corp., 94 F.3d 1553, 1555
(Fed. Cir. 1996). Thus, SimpleAir asserts that the district
court erred in barring assertion of the ’838 and ’048
patents under claim preclusion, as those patents were
never litigated in SimpleAir’s prior actions against
Google’s GCM services. SimpleAir contends that a com-
mon specification and a terminal disclaimer are not
sufficient to presume that distinct patents cover essential-
ly the same invention.
    Google responds that, notwithstanding the fact that
the ’838 and ’048 patents were not previously litigated,
claim preclusion still bars SimpleAir’s latest action.
According to Google, SimpleAir IV involves the same
accused GCM services, as well as materially similar
continuation patents sharing a common specification with
and terminal disclaimers to a common parent patent, as
in SimpleAir I–III. This factual overlap, Google argues,
confirms that the ’838 and ’048 patents are part of the
6                                  SIMPLEAIR, INC.   v. GOOGLE LLC



same cause of action already decided in Google’s favor,
regardless of the precise claim language. Consequently,
Google contends that the district court properly applied
claim preclusion to foreclose SimpleAir’s suit.
                              I.
     Under the doctrine of claim preclusion, “a judgment
‘on the merits’ in a prior suit involving the same parties or
their privies bars a second suit based on the same cause of
action.” Lawlor v. Nat’l Screen Serv. Corp., 349 U.S. 322,
326 (1955). Unlike the related doctrine of issue preclu-
sion, claim preclusion forecloses successive litigation of
the same cause of action whether or not relitigation of the
cause of action involves the same issues as the earlier
suit. New Hampshire v. Maine, 532 U.S. 742, 748–49
(2001). 1
    In assessing claim preclusion, we apply the law of the
regional circuit in which the district court sits, here the
Fifth Circuit. See, e.g., Senju, 746 F.3d at 1348. The test
for claim preclusion in the Fifth Circuit has four ele-
ments: (1) the parties in the later action are identical to,
or in privity with, the parties in the earlier action; (2) the
judgment in the earlier case was rendered by a court with
proper jurisdiction; (3) there has been a final judgment on
the merits; and (4) the earlier case and later case involve
the same cause of action. Duffie v. United States, 600
F.3d 362, 372 (5th Cir. 2010). The only disputed element



    1   When analyzing claim preclusion, courts often use
“claim” and “cause of action” interchangeably. See Senju
Pharm. Co., Ltd. v. Apotex Inc., 746 F.3d 1344, 1349 (Fed.
Cir. 2014). For clarity, “other than in referring to the
name of the doctrine itself, we will use the longer de-
scriptor ‘cause of action’ when discussing claim preclusion
issues; the term ‘claim’ will be used to refer to patent
claims.” Id.
SIMPLEAIR, INC.   v. GOOGLE LLC                           7



in this appeal is whether SimpleAir IV involves the same
cause of action as the prior cases. SimpleAir IV, 204
F. Supp. 3d at 912; Appellant Br. 9–14; Appellee Br. 15.
    “[W]hether a particular cause of action in a patent
case is the same as or different from another cause of
action has special application to patent cases, and we
therefore apply our own law to that issue.” Senju, 746
F.3d at 1348. Our cases generally follow the Restatement
(Second) of Judgments (1982) (hereinafter Restatement),
which defines a cause of action based on the transactional
facts from which it arises. Senju, 746 F.3d at 1349;
Acumed LLC v. Stryker Corp., 525 F.3d 1319, 1323–24
(Fed. Cir. 2008) (citing Restatement § 24); see also Hou-
ston Prof’l Towing Ass’n v. City of Houston, 812 F.3d 443,
447 (5th Cir. 2016) (also applying the Restatement’s
transactional test). In a patent suit, essential transac-
tional facts include both the asserted patents and the
accused activity. Senju, 746 F.3d at 1349; Acumed, 525
F.3d at 1324. If the overlap between the transactional
facts of the suits is substantial, the later action should
ordinarily be precluded. See Restatement § 24 cmt. b.
However, what facts make up a transaction in a given
case “is not capable of a mathematically precise defini-
tion.” Id.
    Because whether a cause of action is barred by claim
preclusion is a question of law, we review de novo the
district court’s dismissal. Acumed, 525 F.3d at 1323; see
also Test Masters Educ. Servs., Inc. v. Singh, 428 F.3d
559, 571 (5th Cir. 2005).
    As an initial matter, we agree with Google that claim
preclusion is not foreclosed because SimpleAir asserted
patents in this case that were not before the district court
in SimpleAir I–III. “What factual grouping constitutes a
‘transaction’ . . . [is] to be determined pragmatically,”
Restatement § 24(2), not through a rigid rule that would
prevent courts from evaluating the extent of factual
8                              SIMPLEAIR, INC.   v. GOOGLE LLC



overlap between cases. We do not interpret the general
statement in Kearns, 94 F.3d at 1555, to be in conflict
with general claim preclusion principles, particularly as
Kearns relied on procedural inadequacies in the earlier
case, id. at 1556, to conclude that claim preclusion did not
apply. While “[o]rdinarily” different patents will raise
different causes of action, Senju, 746 F.3d at 1349 (citing
Kearns, 94 F.3d at 1555), that factor is not dispositive and
does not substitute for the transactional approach con-
sistently followed by this court, see, e.g., id. at 1348–49;
Acumed, 525 F.3d at 1323–24.
    However, although we agree with Google that there is
substantial overlap between SimpleAir IV and SimpleAir
I–III, as the asserted patents all share a common specifi-
cation and terminal disclaimer to a common parent,
ultimately we agree with SimpleAir that the overlap
discussed in the record before us is not sufficient to sus-
tain the district court’s holding of claim preclusion.
     We begin with the maxim that “it is the claims of the
patent which define the invention.” Altoona Publix Thea-
tres, Inc. v. Am. Tri-Ergon Corp., 294 U.S. 477, 487 (1935)
(collecting cases). While the district court concluded that
“the underlying invention is the same” between the pa-
tents asserted throughout SimpleAir I–IV, it never ana-
lyzed the claims of any patent in making that conclusion.
SimpleAir IV, 204 F. Supp. 3d at 913. For its part, Google
argues that while comparison of the patent claims in-
volved in the earlier and later suits may be necessary in
issue preclusion, such comparison is not necessary in
evaluating claim preclusion. Google primarily relies on
Senju for this proposition. See 746 F.3d at 1353.
    In Senju, the patentee in the first case alleged patent
infringement against a defendant, and the district court
held the claims invalid as obvious. Id. at 1347. After-
wards, the patentee amended and added new claims to
the patent in a reexamination proceeding, and then filed a
SIMPLEAIR, INC.   v. GOOGLE LLC                           9



second action for infringement against the same party.
Id. The district court held the patentee’s second action
claim-precluded by the earlier action because it raised the
same cause of action as the first case, as none of the
claims emerging from reexamination were broader than
their predecessors. Id. at 1348.
    On appeal we affirmed, holding that “claims that
emerge from reexamination do not in and of themselves
create a new cause of action that did not exist before.” Id.
at 1352; see Aspex Eyewear Inc. v. Marchon Eyewear, Inc.,
672 F.3d 1335, 1341 (Fed. Cir. 2012). This conclusion
rested in part on 35 U.S.C. § 305, which states “[n]o
proposed amended or new claim enlarging the scope of a
claim of the patent will be permitted in a reexamination
proceeding under this chapter.” Given that statutory
limitation, we rejected the patentee’s argument that it
was necessary in every case to make a detailed compari-
son of the claims. Senju, 746 F.3d at 1352–53.
    Unlike Senju, here the district court did not make any
determination of the scope of the ’838 and ’048 claims in
comparison with the patents litigated in SimpleAir I–III.
Furthermore, there is no prohibition on broadening claims
in continuation patents subject to a terminal disclaimer. 2
So unlike the case of reexamined claims, claims of termi-
nally-disclaimed continuation patents could “provide
larger claim scope to a patentee than the patentee had
under” the parent patent. Senju, 746 F.3d at 1353. In
this sense, continuation patents are more similar to
reissue patents, which we have distinguished from reex-
aminations in the claim preclusion context. See Aspex,
672 F.3d at 1341; 35 U.S.C. § 251(d) (“No reissued patent


    2   Of course, the continuation cannot add new mat-
ter. See, e.g., Applied Materials, Inc. v. Advanced Semi-
conductor Materials, Inc., 98 F.3d 1563, 1579–80 (Fed.
Cir. 1996).
10                             SIMPLEAIR, INC.   v. GOOGLE LLC



shall be granted enlarging the scope of the claims of the
original patent unless applied for within two years from
the grant of the original patent.” (emphasis added)).
Here, given the substantively different requirements of
continuation patents as compared to reexaminations, the
district court erred in holding SimpleAir’s latest suit to be
claim-precluded without any comparison of the asserted
claims to the claims involved in SimpleAir I–III.
    As the accused activity between two cases must be
“essentially the same” for claim preclusion to apply, see
Acumed, 525 F.3d at 1324, we adopt that standard for
comparison of the claims between asserted patents as
well. Thus, where different patents are asserted in a first
and second suit, a judgment in the first suit will trigger
claim preclusion only if the scope of the asserted patent
claims in the two suits is essentially the same. In apply-
ing that standard to the particular context here, we
conclude that claims which are patentably indistinct are
essentially the same.
    Even without any direct analysis of the claims, Google
argues this standard was met here. According to Google,
“the Examiner’s obviousness-type rejection and Sim-
pleAir’s choice to file a terminal disclaimer . . . provided
sufficient evidence that SimpleAir’s terminally-disclaimed
continuation patent claims are not patentably distinct”
from the previously adjudicated claims. Appellant Br. 37.
    We disagree with Google that filing a terminal dis-
claimer settles the issue of claim preclusion here. As the
district court correctly observed, the doctrine of obvious-
ness-type double patenting “was developed to ‘prevent a
patent owner from extending his exclusive right to an
invention through claims in a later-filed patent that are
not patentably distinct from the earlier filed patent,’”
SimpleAir IV, 204 F. Supp. 3d at 913 (quoting Procter &
Gamble Co. v. Teva Pharm. USA, Inc., 566 F.3d 989, 999
(Fed. Cir. 2009)). And filing a terminal disclaimer may
SIMPLEAIR, INC.   v. GOOGLE LLC                           11



obviate an obviousness-type double patenting rejection, 37
C.F.R. § 1.321(c), as it did for the patents at issue, in
exchange for limiting the patent term and alienability of
the resulting continuation patent, see 37 C.F.R.
§§ 1.321(d)(3), 1.321(c)(3). But our cases foreclose the
inference that filing a terminal disclaimer functions as an
admission regarding the patentability of the resulting
claims. See Motionless Keyboard Co. v. Microsoft Corp.,
486 F.3d 1376, 1385 (Fed. Cir. 2007) (“A terminal dis-
claimer is simply not an admission that a later-filed
invention is obvious.”); Ortho Pharm. Corp. v. Smith, 959
F.2d 936, 941 (Fed. Cir. 1992) (rejecting argument that
patent applicant admitted to obviousness-type double
patenting by filing terminal disclaimer); Quad Envtl.
Techs. Corp. v. Union Sanitary Dist., 946 F.2d 870, 874
(Fed. Cir. 1991) (“[T]he filing of a terminal disclaimer
simply serves the statutory function of removing the
rejection of double patenting, and raises neither presump-
tion nor estoppel on the merits of the rejection.”). As a
panel, we lack the authority to deviate from this prece-
dent, and the district court erred by holding otherwise.
    Although a terminal disclaimer does not conclusively
show that a child patent involves the same cause of action
as its parent, the terminal disclaimer is still very relevant
to that inquiry. By filing a terminal disclaimer, a patent
applicant waives potentially valuable rights. We do not
lightly presume that patent applicants forfeit the right to
alienate their patents, and in certain cases years of exclu-
sivity, as a mere procedural expedient. Rather, as oc-
curred here, applicants typically file terminal disclaimers
to overcome obviousness-type double patenting rejections.
In construing the scope of claims, we give considerable
weight to statements made by patent applicants during
prosecution in order to overcome examiner rejections.
See, e.g., Alpex Comput. Corp. v. Nintendo Co. Ltd., 102
F.3d 1214, 1220 (Fed. Cir. 1996). We see no reason to
treat terminal disclaimers any differently.
12                             SIMPLEAIR, INC.   v. GOOGLE LLC



    Thus, a terminal disclaimer is a strong clue that a pa-
tent examiner and, by concession, the applicant, thought
the claims in the continuation lacked a patentable distinc-
tion over the parent. But as our precedent indicates, that
strong clue does not give rise to a presumption that a
patent subject to a terminal disclaimer is patentably
indistinct from its parent patents. It follows that a court
may not presume that assertions of a parent patent and a
terminally-disclaimed continuation patent against the
same product constitute the same cause of action. Rather,
the claim preclusion analysis requires comparing the
patents’ claims along with other relevant transactional
facts.
     While the district court did not specifically consider
the claims, SimpleAir argues on appeal that the claims in
the ’838 and ’048 patents are materially different from
those claims previously litigated in SimpleAir I-III.
Google argues to the contrary, albeit only in discussing
issue preclusion. The primary difference between the
claims of the ’838 and ’048 patents and those in the prior
litigations is the language “whether the selected remote
computing devices are online or offline to the information
providers of the received data,” ’048 patent col. 32 ll. 36–
38; ’838 patent col. 32 ll. 39–41 (emphasis added), as
compared to “whether said computing devices are online
or offline from a data channel associated with each de-
vice.” ’914 patent col. 33 ll. 34–35 (emphasis added). We
held in SimpleAir I that Google did not infringe as a
matter of law because its GCM system “sends messages
over the same communication path as other Internet
data—it does not use a separate path.” 820 F.3d at 431.
SimpleAir has not presented persuasive argument why
“online or offline to the information providers” is different
from “online or offline from a data channel.” Although
SimpleAir argues that the ’838 and ’048 patents disclose a
service that would notify the user’s computer of newly
available information and events of interest when the
SIMPLEAIR, INC.   v. GOOGLE LLC                           13



user’s computer is connected to the Internet but not
connected to the particular information provider, based on
the parties’ limited discussion of the claims on appeal, we
do not see how this is a fundamentally different invention
from those patents asserted in the previous suits. The
’838 and ’048 patents still rely on the same previously
asserted communications architecture with two separate
pathways for online and offline communications.
     Given these similarities between the ’838 and ’048 pa-
tent claims and those of the previously adjudicated pa-
tents, we leave to the district court’s discretion on remand
whether formal claim construction is necessary to resolve
whether the ’838 and ’048 claims are essentially the same
as, i.e., patentably indistinct from, those in the previously
adjudicated parent patents.
    SimpleAir also argues that claim preclusion “does not
bar a cause of action that was never actually asserted in
the prior case,” even if the cause of action could have been
added to the prior case. Appellant Br. 17–18; see Aspex,
672 F.3d at 1344–45 (quoting Gillig v. Nike, 602 F.3d
1354, 1363 (Fed. Cir. 2010)). Because the ’838 and ’048
patents issued after SimpleAir filed its complaints in
SimpleAir II and SimpleAir III, SimpleAir contends that
claim preclusion cannot bar SimpleAir from initiating a
new suit based on those patents.
    SimpleAir’s argument rests on the premise that the
’838 and ’048 child patents constitute causes of action
separate from an earlier adjudication of parent patents.
But as discussed above, assertion of each new continua-
tion patent does not necessarily create a new cause of
action. That is in accordance with Aspex, where we held
that new claims emerging from reexamination did not
create new causes of action and were therefore claim-
precluded, 672 F.3d at 1341, even though the reexamined
claims did not issue until after the first suit had ended,
id. at 1339. Thus, whether the ’838 and ’048 continuation
14                             SIMPLEAIR, INC.   v. GOOGLE LLC



patents present the same cause of action as previously
litigated depends on the scope of their claims, not on their
dates of issuance.
     Claim preclusion implicates both “the weighty policies
of judicial economy and fairness to parties.” United Mine
Workers of Am. v. Gibbs, 383 U.S. 715, 724 (1966). It
“encourages reliance on judicial decisions, bars vexatious
litigation, and frees the courts to resolve other disputes.”
Brown v. Felsen, 442 U.S. 127, 131 (1979). However,
claim preclusion “shields the fraud and the cheat as well
as the honest person,” and “therefore is to be invoked only
after careful inquiry.” Id. at 132.
     The district court made a number of findings that im-
plicate the underlying policies of claim preclusion. It
found that SimpleAir engaged in strategic delay in bring-
ing its fourth suit against Google, SimpleAir IV, 204
F. Supp. 3d at 914, and that SimpleAir previously assured
the jury in SimpleAir I, over four years ago, that it would
not engage in duplicative and burdensome litigation, id.
at 915. Google also alleges on appeal that SimpleAir
coordinated its continuation patent prosecution and
litigation tactics to keep Google perpetually in court. See
Appellee Br. 55.
     While these policy considerations may be persuasive,
it is our duty to faithfully apply our precedent, and that
precedent is inconsistent with the critical premise of the
district court that filing a terminal disclaimer during
prosecution of a continuation patent implies that the
continuation patent is patentably indistinct from its
parent. Our holding in this case is limited to that error:
a district court cannot presume that a terminally-
disclaimed continuation patent presents the same cause
of action as a parent patent based on the filing of the
terminal disclaimer alone. To the extent that the district
court finds that SimpleAir has engaged in improper
SIMPLEAIR, INC.   v. GOOGLE LLC                          15



litigation tactics, the court surely has other means for
dealing with that.
                              II.
    Google alternatively argues that even if claim preclu-
sion does not apply, SimpleAir’s assertion of the ’838 and
’048 patents is precluded by the Kessler doctrine. We
disagree.
    We have held that claim preclusion does not bar a
party from asserting infringement based on activity
occurring after the judgment in the earlier suit. See
Brain Life, LLC v. Elekta Inc., 746 F.3d 1045, 1054 (Fed.
Cir. 2014); see also Aspex, 672 F.3d at 1343. But see
Foster v. Hallco Mfg. Co., Inc., 947 F.2d 469, 472–73, 479–
80 (Fed. Cir. 1991) (indicating that products sold after an
earlier judgment could trigger claim preclusion if they
were “essentially the same” as those in the earlier suit).
However, the so-called Kessler doctrine, 3 named after
Kessler v. Eldred, 206 U.S. 285 (1907), does preclude
assertions of a patent against even post-judgment activity
if the earlier judgment held that “essentially the same”
accused activity did not infringe that patent. See Brain
Life, 746 F.3d at 1057–58. Kessler’s rationale is that the
accused activity, held in the earlier case not to infringe
the patent, acquires a limited trade right to continue
being practiced “without molestation” by the patentee or
its privies. Kessler, 206 U.S. at 285, 290; Brain Life, 746
F.3d at 1058. This doctrine protects “an adjudged non-
infringer” from “repeated harassment for continuing its



    3   It is strange that we now refer to a “Kessler doc-
trine.” There are few doctrines in patent law; not even
the venerable doctrine of equivalents is called the “Graver
Tank doctrine.” So, for Kessler to be elevated to the status
of a doctrine gives it rare standing. Nonetheless, we will
not buck the rising tide.
16                            SIMPLEAIR, INC.   v. GOOGLE LLC



business as usual post-final judgment.” Id. at 1056 (em-
phasis in original).
    In Brain Life, we held assertion of the same set of pa-
tent claims barred by both claim preclusion, id. at 1053,
and the Kessler doctrine, id. at 1058–59. We relied on the
Kessler doctrine only to bar assertion of the claims at
issue against essentially the same products made or sold
after the judgment of noninfringement in the earlier case,
id. at 1058, i.e., products that claim preclusion could not
reach because of their timing, id. at 1054. In contrast, we
have not applied the Kessler doctrine to bar a broader set
of rights than would be barred by claim preclusion. Nor
have we applied the Kessler doctrine to activity predating
the earlier judgment, as Google advocates here, Appellee
Br. 53. In effect, Google asks us to subsume claim preclu-
sion within a more expansive, sui generis Kessler doctrine.
But the Kessler doctrine just fills a particular temporal
gap between preclusion doctrines, see Brain Life, 746 F.3d
at 1056; it does not displace them.
    However, as in the claim preclusion context, we also
disagree with SimpleAir’s argument that the Kessler
doctrine cannot in any case bar assertion of terminally-
disclaimed continuation patents when only parent patents
have previously been held noninfringing. If, on remand,
the district court determines that the claims of the ’838
and ’048 patents are patentably indistinct from those
previously adjudicated, and are therefore claim-precluded
with respect to pre-judgment GCM services, then the
Kessler doctrine would also bar SimpleAir’s assertions of
those patents against Google’s provision of essentially the
same GCM services post-judgment.
                           III.
    Google also argues that issue preclusion bars Sim-
pleAir’s assertion of the ’838 and ’048 patents. Google did
not raise issue preclusion before the district court, and
accordingly the district court never addressed it. General-
SIMPLEAIR, INC.   v. GOOGLE LLC                         17



ly, “those issues not raised below at the district court
cannot be heard for the first time on appeal.” Conoco, Inc.
v. Energy & Envtl. Int’l., 460 F.3d 1349, 1358 (Fed. Cir.
2006). Google has not presented any circumstances that
warrant deviating from normal rules of waiver. We thus
conclude that Google waived its issue preclusion argu-
ment.
                         CONCLUSION
    For the foregoing reasons, we vacate the district
court’s order and remand for further proceedings con-
sistent with this opinion.
             VACATED AND REMANDED
