                             In the

    United States Court of Appeals
                For the Seventh Circuit
No. 15-2686
UNITED STATES OF AMERICA,
                                               Plaintiff-Appellee,
                               v.

LESHAWN STANBRIDGE,
                                            Defendant-Appellant.



            Appeal from the United States District Court
                  for the Central District of Illinois.
      No. 14-cr-30020-SEM-TSH-1 — Sue E. Myerscough, Judge.



  ARGUED JANUARY 26, 2016 — DECIDED FEBRUARY 23, 2016



   Before WOOD, Chief Judge, and BAUER and POSNER, Circuit
Judges.
    BAUER, Circuit Judge. LeShawn Stanbridge appeals his
conviction for possession of methamphetamine with intent
to distribute, 21 U.S.C. § 841(a)(1). The drugs had been found
in Stanbridge’s car after police in Quincy, Illinois, detained
him on the ground that he committed a traffic offense by not
signaling continuously for 100 feet before pulling alongside
the curb to park. That understanding of Illinois law was
2                                                  No. 15-2686

wrong, but the district court decided that the mistake was
reasonable and, for that reason, denied Stanbridge’s motion
to suppress the drugs. We hold that the mistake of law was
not reasonable, and thus Stanbridge’s motion to suppress
should have been granted.
                       I. BACKGROUND
    Stanbridge was walking to his car carrying a duffel bag
when two Quincy police officers passed by on patrol. Stan-
bridge hesitated and looked surprised when he saw the of-
ficers, so they circled the block and began shadowing him
with the hope of catching him in a traffic violation. After
driving just a short distance, Stanbridge activated his right
turn signal, pulled to the side of the street, and parked paral-
lel with the curb. Officer Steve Bangert, who was driving,
had not witnessed any traffic violation before Stanbridge
pulled over, but his partner, Officer Paul Hodges, later re-
ported that Stanbridge had turned left at an intersection
without signaling while being followed. Unaware of his
partner’s observation, Bangert stopped behind Stanbridge
and activated his blue flashers, effectively seizing Stan-
bridge. Bangert did so because Stanbridge had not activated
his turn signal 100 feet before pulling to the curb.

    Stanbridge had a valid driver’s license, but a check for
criminal history showed that he “did have priors,” prompt-
ing Officer Bangert to request a drug-sniffing dog (though
Stanbridge’s only drug conviction was for marijuana posses-
sion, 11 years earlier when he was 17). The dog arrived
10 minutes later, and its alert led to the discovery of meth-
amphetamine, marijuana, and pills inside Stanbridge’s duf-
fel bag. He was arrested and confessed to acting as a “mid-
No. 15-2686                                                3

dleman” for two suppliers who had trafficked six pounds of
methamphetamine in as many months.

    Stanbridge was charged with conspiracy to distribute a
controlled substance, 21 U.S.C. §§ 846, 841(a)(1), and posses-
sion with intent to distribute, id. § 841(a)(1). He moved to
suppress the evidence derived from the stop, asserting that
he was seized unlawfully because he had not committed a
traffic violation. The government responded that the police
officers had two bases for seizing Stanbridge: He did not ac-
tivate his turn signal 100 feet before pulling over to park,
and he had made a left turn without signaling at all. Video
from a dashcam in the officers’ patrol car confirms that Stan-
bridge did not signal for 100 feet before parking, but, the
government conceded, the illegal left turn cannot be seen in
the video.

    At a hearing on Stanbridge’s motion to suppress, both
police officers testified, and the dashcam video was played.
Officer Bangert acknowledged that he had not seen Stan-
bridge commit a traffic violation before the alleged turn-
signal violation when parking. Indeed, Bangert’s only justifi-
cation for detaining Stanbridge was that he had “started to
signal after [his car] already started its turn pulling to the
curb.” Officer Hodges, on the other hand, testified that he
had seen Stanbridge turn left at an intersection without sig-
naling; he didn’t mention this violation to Bangert when it
occurred, he added, because he had assumed that his part-
ner also witnessed the illegal turn.

     Stanbridge’s car did not come in view of the dashcam un-
til just before he parked. Stanbridge was on a street without
4                                                  No. 15-2686

lane markings, with no other traffic in sight (except for the
officers’ car). But the video does confirm that Stanbridge ac-
tivated his turn signal just before he pulled to the right to
park, not contemporaneously with the rightward movement
as described by the police officers.

    The district court denied Stanbridge’s motion in a written
order. The court assumed that Officer Hodges had seen
Stanbridge make an unsignaled left turn. But that observa-
tion, the court reasoned, would have given Hodges, not Of-
ficer Bangert, probable cause to make a traffic stop:

      Officer Hodges … was not driving the po- lice
      car and did not initiate the traffic stop. Of- ficer
      Bangert, as the driver, did, but Officer Bangert
      testified that he did not see Stan- bridge’s left
      turn without a proper signal. Moreover, both
      officers testified that Officer Hodges did not tell
      Officer Bangert about Stanbridge’s unsignaled
      left turn, and Officer Hodges testified that he
      had assumed that Of- ficer Bangert saw the turn
      for himself.

Thus, the court concluded, the left turn was irrelevant, and
only Bangert’s explanation for detaining Stanbridge could
justify the defendant’s seizure. The court opined that the Il-
linois Vehicle Code is ambiguous (and noted that courts in
the state had not offered guidance) concerning whether a
driver must signal for 100 feet before pulling to a curb. And,
the district court concluded, Bangert’s belief “was reasona-
ble, even if it were mistaken,” and thus the perceived ambi-
guity “must be resolved in the Government’s favor.
No. 15-2686                                                5

    Stanbridge then entered a conditional guilty plea to the
count charging him with possessing the methamphetamine
in his duffle bag, while reserving the right to challenge on
appeal the denial of his motion to suppress. See FED. R. CRIM.
P. 11(c)(1)A), (B). He was sentenced to 144 months’ impris-
onment.

                       II. DISCUSSION

    In this court Stanbridge argues that Illinois law does not
require a driver to signal continuously for 100 feet before
parking parallel to a curb, and that Officer Bangert’s mistake
of law on this point was unreasonable and thus cannot be a
basis for upholding the seizure. The government counters
that Stanbridge’s challenge is not properly before us be-
cause, according to the government, in briefing this appeal
he neglected to contest a second reason given by the district
court for denying his motion to suppress. We therefore begin
with the government’s contention that Stanbridge has com-
mitted waiver.

    In opposing Stanbridge’s motion in the district court, the
government asserted that his failure to signal before turning
left at an intersection, as seen by Officer Hodges but not cap-
tured on the dashcam video, provided a basis for the seizure
independent of Stanbridge’s actions while parking. On ap-
peal, the government’s primary contention is that Stanbridge
has waived any challenge to his initial detention by not ad-
dressing what the government characterizes as “the district
court’s unmistakable finding” of probable cause to seize him
based on the unsignaled left turn. In his opening brief Stan-
bridge discusses only Officer Bangert’s justification for the
6                                                 No. 15-2686

seizure, and thus, the government argues, Stanbridge has
left unchallenged an alternative rationale for sustaining his
initial detention. This “omission,” the government insists, “is
fatal to his appeal.”

    To the contrary, waiver is a problem for the government,
not Stanbridge. That is because the government’s premise
rests entirely on its untenable reading of the district court’s
ruling. The court’s order, in the opening paragraph, does
talk about improperly signaled “turns” giving the “officers”
probable cause to make a traffic stop. Yet despite these plu-
ral references, the court’s decision later makes clear that the
judge did not accept the government’s contention that it
could rely on both “turns” to justify the detention of Stan-
bridge. The government correctly observes that the district
court thought that Officer Hodges’s observation of Stan-
bridge turning left at an intersection without signaling pro-
vided Hodges with probable cause for a traffic stop, but the
government omits what the court said next:

      Officer Hodges, however, was not driving the
      police car and did not initiate the traffic stop.
      Officer Bangert, as the driver, did, but Officer
      Bangert testified that he did not see Stan-
      bridge’s left turn without a proper signal.
      Moreover, both officers testified that Officer
      Hodges did not tell Officer Bangert about
      Stanbridge’s unsignaled left turn, and Officer
      Hodges testified that he had assumed that Of-
      ficer Bangert saw the turn for himself.
No. 15-2686                                                 7

The district court thus believed that only Officer Bangert, the
driver of the patrol car, had effectuated Stanbridge’s seizure
and thus only his rationale and the facts known to him mat-
tered. In so doing, the district court rejected the government’s
reliance on the unsignaled left turn as a justification for the
initial detention.

     The government may disagree with the district court’s
reasoning, but it does not argue in its brief that we should
reject that reasoning and view the left turn as an alternative
basis for upholding the stop of Stanbridge. By instead mis-
construing the court’s order and arguing that Stanbridge has
engaged in waiver, the government has failed to recognize,
let alone challenge, the district court’s rejection of its posi-
tion that the stop was alternatively justified by the un-
signaled left turn. The government, like other litigants, can
waive its opportunity to challenge an adverse ruling on an
argument presented to the district court. See United States v.
Cherry, 436 F.3d 769, 772 (7th Cir. 2006) (recognizing that
government “inexplicably abandoned reliance” on valid jus-
tification for vehicle search by failing to challenge district
court’s rejection of that ground presented at suppression
hearing); United States v. Wilson, 390 F.3d 1003, 1009–10 (7th
Cir. 2004) (refusing to review factual assertions where gov-
ernment failed to challenge district court’s rejection of those
same contentions); United States v. Dyer, 580 F.3d 386, 390
(6th Cir. 2009) (finding waiver where government failed to
challenge district court’s determination that defendant had
standing to bring Fourth Amendment claim). The govern-
ment has not asked us to reject as unsound the district
court’s conclusion that only Officer Bangert, not the “team,”
seized Stanbridge, and that Officer Hodges’s observation
8                                                   No. 15-2686

cannot be considered. The government’s oversight in failing
to argue the issue is so large that we conclude it has waived
reliance on the left turn as a justification for Stanbridge’s sei-
zure.

   That leaves Stanbridge’s challenge to the sole ground on
which the district court did rely: He did not signal for
100 feet before pulling to the curb to park. Section 11-804 of
the Illinois Vehicle Code provides:

       When signal required. (a) No person may turn
       a vehicle at an intersection unless the vehicle is
       in proper position upon the roadway as re-
       quired in Section 11-801 or turn a vehicle to en-
       ter a private road or driveway, or otherwise
       turn a vehicle from a direct course or move
       right or left upon a roadway unless and until
       such movement can be made with reasonable
       safety. No person may so turn any vehicle
       without giving an appropriate signal in the
       manner hereinafter provided.

       (b) A signal of intention to turn right or left
       when required must be given continuously
       during not less than the last 100 feet traveled
       by the vehicle before turning within a business
       or residence district, and such signal must be
       given continuously during not less than the
       last 200 feet traveled by the vehicle before turn-
       ing outside a business or residence district.
No. 15-2686                                                9

      (c) No person may stop or suddenly decrease
      the speed of a vehicle without first giving an
      appropriate signal in the manner provided in
      this Chapter to the driver of any vehicle im-
      mediately to the rear when there is opportuni-
      ty to give such a signal.

      (d) The electric turn signal device required in
      Section 12-208 of this Act must be used to indi-
      cate an intention to turn, change lanes or start
      from a parallel parked position but must not be
      flashed on one side only on a parked or disa-
      bled vehicle or flashed as a courtesy or “do
      pass” signal to operators of other vehicles ap-
      proaching from the rear. However, such signal
      devices may be flashed simultaneously on both
      sides of a motor vehicle to indicate the pres-
      ence of a vehicular traffic hazard requiring un-
      usual care in approaching, overtaking and
      passing.

625 ILCS 5/11-804. Stanbridge disagrees with the district
court’s belief that this statute is ambiguous concerning the
100-foot minimum signaling distance. Stanbridge is willing
to concede that moving from a traffic lane to a curb is a lane
change governed by § 11-804(d), but even so, he argues, the
statute requires only that a signal “must be used” when
changing lanes, not that a signal be used for 100 feet or any
other specified distance. In response, the government has
abandoned its previous argument that pulling to a curb con-
stitutes a “turn” requiring a 100-foot warning, and instead
the government argues that a “driver cannot ‘indicate an in-
10                                                No. 15-2686

tention’ to change lanes while he is already changing lanes,”
because to do so would fail to give other drivers sufficient
notice and defeat the statute’s purpose.

    We agree with Stanbridge that § 11-804 is not ambiguous,
and does not require a driver to signal for 100 feet before
pulling alongside a curb to park. The minimum signaling
distances required by subsection (b) apply only when a driv-
er intends “to turn right or left” (emphasis added). And no
other subsection includes an explicit command to signal be-
fore moving toward a curb to park. As the district court not-
ed, “[i]f the Illinois General Assembly had meant for the sig-
nal requirement to apply to a motorist pulling to a stop at
the curb under § 11-804(d), it knew how to do so explicitly,
as § 11-804(d) clearly requires the use of a turn signal before
‘start[ing] from a parallel parked position’.” This is a sensi-
ble reading of the statute, and the government has not given
us reason to think that the legislature intended to require
drivers seeking parking in congested urban areas to contin-
uously signal for 100 feet before determining that a possible
parking space is not only large enough, but also free of fire
hydrants, yellow curbs, and other parking restrictions.

     So the only possible relevance of § 11-804 is the require-
ment in subsection (d) that a signal be used to indicate an
intention to “change lanes.” “Lane” is not defined (and the
Illinois courts have not had occasion to construe the term,
especially as applied to an unstriped roadway). But even if
moving toward the curb of unstriped pavement to park con-
stitutes “changing lanes,” § 11-804(d) requires only that a
turn signal “be used.” And Stanbridge did use his signal, as
the government is compelled to acknowledge. What’s more,
No. 15-2686                                                  11

the dashcam video refutes the government’s assertion that
Stanbridge activated his turn signal only after pulling to-
ward the curb; the light was on before Stanbridge moved to
the right.

    This does not end our inquiry, however, because a police
officer’s objectively reasonable mistake of law can provide rea-
sonable suspicion for a seizure. See Heien v. North Carolina,
135 S. Ct. 530, 534–35, 539–40 (2014) (concluding that police
officer’s mistaken belief that ambiguous vehicle code re-
quired more than one functional brake light was objectively
reasonable). The district court concluded that Officer
Bangert was objectively reasonable, even if mistaken, in be-
lieving that § 11-804 requires motorists to signal for at least
100 feet before pulling to a curb. Rather than defend this
conclusion, the government in its brief dismisses as an “aca-
demic proposition” Stanbridge’s argument that the district
court erred.

    We view the government’s silence as an implicit conces-
sion that, as Stanbridge maintains, Officer’s Bangert’s mis-
understanding of § 11-804 was not objectively reasonable.
The statute isn’t ambiguous, and Hein does not support the
proposition that a police officer acts in an objectively reason-
able manner by misinterpreting an unambiguous statute.
See United States v. Flores, 798 F.3d 645, 649–50 (7th Cir. 2015)
(concluding that police officer could not reasonably have be-
lieved that motorist’s use of license-plate frame found on
“vast” number of cars violated Illinois statute). The 100-foot
requirement in § 11-804(b) unambiguously applies to turns,
and nothing more. Bangert simply was wrong about what
the provision required, yet “an officer can gain no Fourth
12                                                 No. 15-2686

Amendment advantage through a sloppy study of the laws
he is duty-bound to enforce.” Hein, 135 S. Ct. at 539–40.

    The government suggests that we disregard whether Of-
ficer Bangert acted reasonably and instead declare that Stan-
bridge violated § 11-804 for a reason unrelated to the 100-
foot signaling minimum. In the government’s eyes, Stan-
bridge signaled “too late” and failed to give adequate warn-
ing to other drivers. For this proposition the government re-
lies on the requirement in § 11-804(c) that drivers give notice
to vehicles directly behind them before suddenly decreasing
speed if “there is opportunity to give such a signal.” The
government also echoes the district court’s statement that
“the overall purpose of the statute is plainly to regulate the
movement of vehicles and to provide notice of that move-
ment to other motorists.”

    It should suffice to note that this argument wasn’t made
in the district court and is thus forfeited. See, e.g., United
States v. Dachman, 743 F.3d 254, 259 (7th Cir. 2014); Fryer v.
United States, 243 F.3d 1004, 1011–12 (7th Cir. 2001). Anyway,
who else was on the road to warn? Once again the dashcam
video upends the government’s contention; as is plain from
that video, the police officers’ distant patrol car was the only
other vehicle in sight of Stanbridge, and he already was
moving slowly when he decided to pull over and park.

                       III. CONCLUSION

   Stanbridge fully complied with § 11-804. Officer
Bangert’s contrary belief was not objectively reasonable, and
thus the officer’s mistake of law cannot justify Stanbridge’s
No. 15-2686                                               13

seizure. Accordingly, the denial of the defendant’s motion to
suppress must be overturned. The judgment of conviction is
VACATED, and the case is REMANDED to the district court
for further proceedings.
