SCHUMAN, J.

This case is before us on remand from the Supreme Court. State v. Kurokawa-Lasciak, 351 Or. 179, 263 P.3d 336 (2011) (Kurokawa-Lasciak II). In our original opinion, State v. Kurokawa-Lasciak, 237 Or.App. 492, 498, 239 P.3d 1046 (2010) (Kurokawa-Lasciak I), we held that a law enforcement officer's warrantless search of defendant's van, leading to the discovery of various controlled substances, did not violate Article I, section 9, of the Oregon Constitution, because the search fell within one of the exceptions to the warrant requirement—the so-called "automobile exception." Because we held that the search was valid under that exception, we did not reach the state's alternative argument that the search was also valid because defendant's companion consented to it. The Supreme Court reversed, holding that the search did not fall within the automobile exception, and remanded the case for us to consider the state's argument that the police had valid consent. Kurokawa-Lasciak II, 351 Or. at 193, 263 P.3d 336. We now conclude that defendant's companion lacked authority to consent to a search of the vehicle and, for that reason, the search was unlawful. We therefore affirm the trial court's suppression of evidence that the search disclosed.

The following facts are consistent with the trial court's findings and its decision to grant defendant's motion to suppress. State v. Meharry, 342 Or. 173, 175, 149 P.3d 1155 (2006) (stating standard). Defendant, his companion Campbell, and their three children were at the Seven Feathers Casino, where defendant was gambling. A casino employee monitoring defendant's conduct noticed that he would buy chips with small-denomination bills, play casino games, and then cash in the chips for large-denomination bills. The employee suspected that defendant was engaged in money laundering. As a result, the casino barred defendant from further cash transactions and posted his photograph in the cashiers' cages. When a cashier later refused to carry out a cash transaction for defendant, he reached through the cage, grabbed his photo, and left the casino. A casino employee telephoned a state trooper, Bennett, and reported that defendant had stolen casino property—the photograph.

Shortly thereafter, a different officer, Wohls, detained defendant for questioning in the casino parking lot as defendant was walking away from a van. Bennett, the trooper, arrived at the scene and also spoke to defendant. He asked defendant about the van and whether it contained drugs. When defendant did not respond, Bennett arrested him for disorderly conduct and third-degree theft; he also asked defendant for consent to search the van. Defendant refused. Bennett then told defendant that he could either consent to a search of the van or be taken to jail for disorderly conduct and theft. Defendant responded that he did not believe that Bennett's offer was sincere. Bennett then repeated his request to search the van, and also requested consent to search defendant's pockets and the room at the casino where defendant was staying. The Supreme Court related the remaining facts as follows:

Kurokawa-Lasciak II, 351 Or. at 183-84, 263 P.3d 336.

Based on those facts, defendant was charged with delivery of a controlled substance, ORS 475.840, possession of marijuana, ORS 475.864, money laundering, ORS 164.170, third-degree theft, ORS 164.043, and second-degree disorderly conduct, ORS 166.025. He moved to suppress the evidence discovered in the search, citing Article I, section 9, of the Oregon Constitution. The trial court granted the motion, reasoning that, under the United States Supreme Court's opinion in Georgia v. Randolph, 547 U.S. 103, 126 S.Ct. 1515, 164 L.Ed.2d 208 (2006), Campbell lacked authority to consent to the search of the van after defendant had previously refused permission. In Randolph, 547 U.S. at 106, 126 S.Ct. 1515, the Court held that "a physically present co-occupant's stated refusal to permit entry prevails" over the voluntary consent of the other occupant. On the state's appeal, this court determined that the warrantless search was permitted by the automobile exception. Kurokawa-Lasciak I, 237 Or.App. at 499, 239 P.3d 1046. We therefore did not reach the state's contention that the search was permitted based on Campbell's consent.

The Supreme Court disagreed with our conclusion that the search was permitted under the automobile exception, explaining that the automobile exception did not apply because the vehicle was not mobile at the time police first encountered it in connection with a crime. Kurokawa-Lasciak II, 351 Or. at 194, 263 P.3d 336. The court remanded the case to us for consideration of the state's alternative argument that the warrantless search was authorized by Campbell's consent. We now address that issue.

The United States Supreme Court's decision in Randolph, and whether it extends to consent obtained over the refusal of a nonpresent co-occupant of a vehicle instead of a dwelling, is relevant in this case only if we decide that defendant's rights were not protected under Article I, section 9, of the Oregon Constitution. For that reason, we begin our analysis with the state constitutional question. Sterling v. Cupp, 290 Or. 611, 614, 625 P.2d 123 (1981) (when state's law protects person's rights, no federal question arises).1 Because, as explained below, we conclude that the search in this case violated Article I, section 9, we affirm the trial court without reaching the federal question.

The general rule governing third-party consent has not changed significantly since 1983, when the Oregon Supreme Court in State v. Carsey, 295 Or. 32, 44, 664 P.2d 1085 (1983), adopted the rule from United States v. Matlock, 415 U.S. 164, 94 S.Ct. 988, 39 L.Ed.2d 242 (1974).

Carsey, 295 Or. at 44-46, 664 P.2d 1085. Although Carsey was decided under the Fourth Amendment, we subsequently adopted the same rule under Article I, section 9, holding that "common authority to validly consent to a search `rests on mutual use of the property by persons generally having joint access or control for most purposes.'" State v. Will, 131 Or.App. 498, 504, 885 P.2d 715 (1994) (quoting Matlock, 415 U.S. at 171 n. 7, 94 S.Ct. 988). The state has the burden of proving by a preponderance of the evidence that the consenting person has the requisite authority. City of Portland v. Paulson, 98 Or.App. 328, 330, 779 P.2d 188 (1989). We defer to the trial court's express and implicit findings of fact, but whether those facts support a conclusion that the consenting person had authority is a legal question. State v. Beylund, 158 Or.App. 410, 417, 976 P.2d 1141, rev. den., 328 Or. 594, 987 P.2d 515 (1999).

The rule from Carsey onward has derived principally from the idea that one joint occupant of premises has for most purposes assumed the risk that another occupant might permit a search of those premises. Matlock, 415 U.S. at 171 n. 7, 94 S.Ct. 988; Carsey, 295 Or. at 44, 664 P.2d 1085; State v. Fuller, 158 Or.App. 501, 506, 976 P.2d 1137 (1999) ("Central to search and seizure law is whether an individual has, in some way, assumed the risk that a third party may legally consent to a search of that individual's property."); Beylund, 158 Or. App. at 418, 976 P.2d 1141 ("[D]efendant legally assumed the risk that [his tenant], the person he placed in charge of his property, would consent to a search."). Consequently, we have repeatedly held that the scope of a person's authority depends on the level of access that the co-occupants have agreed on. Thus, when there is no evident agreement to the contrary, one co-occupant is presumed to have completely assumed all risk that the other will consent to a search; the other has a full quantum of authority. For example, in Beylund, 158 Or.App. at 418, 976 P.2d 1141, we held that the defendant "legally assumed the risk" that his tenant would consent to a search because the tenant "had full access to the shop basement and entered it regularly to tend the marijuana plants. There is no contrary evidence." (Emphasis added.) Likewise, in State v. Surface/Hurley, 183 Or.App. 368, 374-75, 51 P.3d 713 (2002), we held that the defendants expressly gave house-sitters full control of "the household and everything pertaining to it," and, consequently, the house-sitters had "actual authority" over the defendants' freezer and "could lawfully consent to a search of it."

Conversely, we have also held that, where a defendant has expressly or by implication limited a co-occupant's authority, the resulting consent depends on whether the search is within that limited authority. In Carsey, 295 Or. at 43, 664 P.2d 1085, for example, the Supreme Court held that police could not rely on a grandmother's consent to search her grandson's room in the house that they shared because the evidence indicated that the defendant had not granted his grandmother control over the room. In Fuller, 158 Or.App. at 506, 976 P.2d 1137, we held that, although the defendant and his girlfriend shared not only a house but a bedroom, and the girlfriend had authority to consent to a general search of the premises, the evidence indicated that she did not have authority to consent to a search of the defendant's nightstand. Even within a parent-child relationship, we have held, "the presence or absence of common authority hinges, necessarily, on the particular agreement between parent and child. Thus, whether defendant's parents had common authority to consent to the search of the garage here turns on their specific agreement with defendant regarding his use of the garage." State v. Jenkins, 179 Or.App. 92, 101, 39 P.3d 868, rev. den., 334 Or. 632, 54 P.3d 1042 (2002).2

Under these precepts, the consent issue in this case reduces to the question of whether defendant and Campbell had an understanding that Campbell had common access to and control of the van when she gave Bennett consent to search it. The trial court, relying on a federal case under the Fourth Amendment (United States v. Morales, 861 F.2d 396 (3rd Cir.1988)), ruled that Campbell had authority to consent (although, as noted, the court also ruled that that consent was superseded by defendant's refusal). We do not find Morales helpful. The only issue in that case was whether a person who is the driver, but not the lessee, of a rental car, can consent to a search of the entire car, and the court based its decision on the fact that Morales, as the nonlessee driver, had immediate possession of and control over the car: "By giving Morales control over the car, [the actual lessee] conferred on Morales power to consent to a reasonable search of it." Id. at 399. No such delegation of control exists on the facts of this case.3 The only evidence that Campbell had control of defendant's van was the fact that he had given her the key. However, as we have previously held, mere possession of the key to premises does not necessarily indicate complete access or control. Fuller, 158 Or.App. at 506, 976 P.2d 1137 (consenting co-occupant had key, but nonetheless lacked authority to consent to search of nightstand).

The evidence in this case establishes that, although defendant gave Campbell the key to the van (and to that extent gave her control and access) the control and access were very narrowly limited—so much so that we conclude without difficulty that the access and control did not encompass consent to search. As Campbell and Bennett both testified, defendant gave Campbell the key after defendant had refused consent to search, after he was arrested, and when he knew that he was being taken away from the casino. Under those circumstances, he told Campbell to, "lock the van, take care of the family dog, go to the casino's restaurant to eat, and stay put until he returned." Kurokawa-Lasciak II, 351 Or. at 183, 263 P.3d 336. Regarding those instructions, Campbell testified, "He gave me the keys, and he said, `[c]ome check on the dog, lock it up, and don't go anywhere, just wait for me.'"

Until Bennett persuaded her to the contrary, Campbell clearly believed that she did not have authority beyond extracting the family dog, locking the van, and keeping it locked. We conclude that her belief was correct; defendant's instructions, in light of his circumstances, can only be construed as imposing strict limitations on Campbell's access to the van, and those limitations did not encompass consenting to a search. Put another way, if defendant had ever assumed the risk that Campbell might have consented to allow a police officer to search the van, he negated that assumption with his instructions to her.

We therefore conclude that, when Bennett obtained consent to search, that consent was not authorized. Because the search of the van was not lawful under the automobile exception or the consent exception and the state suggests no other justification, the evidence that was seized from the van was unlawfully obtained. The trial court did not err in granting defendant's motion to suppress.

Affirmed.