Opinion by Judge LEAVY; Partial Concurrence and Partial Dissent by Judge REINHARDT.
OPINION
LEAVY, Circuit Judge:FACTS AND PRIOR PROCEEDINGS
This case arose when the appellant, Robert Lee Zimmerman, was arrested for trespass while a house guest of the Kanes, who were squatters in a shack on property owned by the Bishop Estate of Hawaii. In early 1988, the Kanes moved onto the property. In March 1988, Mrs. Kane’s father wrote to the Bishop Estate and requested permission for his daughter to be appointed caretaker of the property. Permission was declined in April 1988. In June 1988, the Bishop Estate sent the Kanes a letter warning them that they were trespassing by residing on the property and that they had to vacate. The letter was followed by visits by Elaine Dung Brown, the Bishop Estate land manager, and by Peter Bertulfo, the caretaker appointed by the Estate. Bertulfo, a police officer, entered into a tenancy agreement with the Bishop Estate on October 24, 1988.
On October 26, 1988, Brown and Bertulfo went to the property and warned the Kanes that they had to leave. The family agreed to vacate in five days. On October 31, 1988, Brown and Bertulfo returned with a police officer and after discussion, they agreed to allow the Kanes one more day to vacate the premises. On November 1,1988, Brown and Bertulfo returned with police officers, who warned the Kanes and their guests, including *787Zimmerman, that they were trespassing. Everyone left, except Mrs. Kane and Zimmerman, who were arrested. They were taken to the police station, charged with trespass in the second degree and released on bail.
Mrs. Kane then moved back on the property, prompting the Bishop Estate to file an action for ejectment. The Kanes then moved from the premises. The criminal trespass proceedings against Mrs. Kane and Zimmerman were dropped.
In February 1990, Zimmerman filed this pro se action against the Bishop Estate, its trustees, and certain city and county officials. The amended complaint alleged a civil rights violation under 42 U.S.C. § 1983, a conspiracy to violate civil rights, and supplemental state claims.1 The district court granted summary judgment to the Bishop Estate and to the city and county defendants. The district court also granted the Bishop Estate’s motion for attorney’s fees and sanctions pursuant to 42 U.S.C. § 1988 and Fed.R.Civ.Proc. 11.
Zimmerman, appearing pro se, appeals the district court’s summary judgments in favor of the Bishop Estate and the Bishop Estate Trustees and employees (the private defendants), and the mayor of Honolulu, the City and County of Honolulu, the former and acting chiefs of police, two prosecutors, and various other municipal and county employees (the city defendants). Zimmerman argues that the district court erred by (1) determining that there was no constitutional violation under 42 U.S.C. § 1983; (2) dismissing Zimmerman’s supplemental state tort claims; (3) granting protective orders as to his discovery requests; (4) denying his motions to recuse the district court judge and magistrate judge; and (5) bifurcating his punitive damages claim. Zimmerman also appeals the district court’s award of sanctions and attorney’s fees to the private defendants.
We affirm the district court on the merits, affirm the award of sanctions regarding Zimmerman’s improper motives, and reverse the award of sanctions on the malicious prosecution claim.
DISCUSSION
1. 42 U.S.C. § 1983 Claim
Zimmerman argues that the warrantless arrest violated his Fourth Amendment rights as a guest and that there were no exigent circumstances to justify the search. A party invoking Fourth Amendment protection must have a subjective expectation of privacy that is objectively reasonable. United States v. Taketa, 923 F.2d 665, 670 (9th Cir.1991).
Zimmerman contends that the Kanes had an expectation of privacy because of the length of residency, their improvement of the property and the private defendants’ acquiescence in the Kanes’ presence. There is no evidence that the Kanes owned, rented, or leased the land or the residence. The private defendants were subsequently given summary possession of the parcel in state court proceedings.
Even if Mrs. Kane had a subjective expectation of privacy, her expectation was not objectively reasonable. In Amezquita v. Hernandez-Colon, 518 F.2d 8, 11-12 (1st Cir.1975), cert. denied, 424 U.S. 916, 96 S.Ct. 1117, 47 L.Ed.2d 321 (1976), the court held that squatters had no reasonable expectation of privacy where they had no legal right to occupy the land and build structures on it. Similarly, the Tenth Circuit has concluded that the Fourth Amendment rights of a trespasser living on federal land were not violated because he had no reasonable expectation of privacy. United States v. Ruckman, 806 F.2d 1471, 1472-74 (10th Cir.1986).
Here, the Kanes requested, and were denied, permission to reside on the property. Three months later they were informed by letter that they were trespassing. In later visits they were told that they were trespassing. There is no dispute of material fact regarding the ownership of the property or whether the private defendants acquiesced in the presence of the Kanes. As a guest on the property, Zimmerman had no greater *788right to be on the property than did the Kanes. The Kanes’ improvement of the property does not give rise to a reasonable expectation of privacy when they had no legal right to occupy the land. See Amezquita, 518 F.2d at 12.
Even if we assume that Zimmerman and the Kanes had an expectation of privacy that was objectively reasonable, Zimmerman’s constitutional rights were not violated because the arrest was lawful. There is no Fourth Amendment violation if the officers have obtained the consent of a third party who possesses common authority over the premises. United States v. Matlock, 415 U.S. 164, 171 & n. 7, 94 S.Ct. 988, 993 & n. 7, 39 L.Ed.2d 242 (1974). The police were provided with evidence of the private defendants’ ownership of the property at the time of the arrest. Moreover, even if the private defendants did not have actual authority over the premises, the arrest was valid because the police, at the time of the entry, reasonably believed they did have authority over the premises. See Illinois v. Rodriguez, 497 U.S. 177, 188-89, 110 S.Ct. 2793, 2801-02, 111 L.Ed.2d 148 (1990). Because we conclude that there is no evidence of a constitutional violation, we do not decide whether the private defendants acted under color of state law.
We also affirm the district court’s grant of summary judgment to the city defendants on the federal claims because there is no evidence that Zimmerman’s constitutional rights were violated. See Palmerin v. Riverside, 794 F.2d 1409, 1414-15 (9th Cir.1986) (absent any constitutional violations by individual defendants, there can be no municipal liability).
2. Supplemental State Claims
In his amended complaint, Zimmerman alleges several state tort claims. We review the district court’s determination of state law de novo. In re McLinn, 739 F.2d 1395, 1397 (9th Cir.1984) (en banc).
a. Malicious Prosecution
Under Hawaii law, a warrantless arrest is lawful if a police officer has probable cause to believe that an offense is being committed in the officer’s presence. House v. Ane, 56 Haw. 383, 538 P.2d 320, 325 (1975). Hawaii agrees with the rule in Amezquita, 518 F.2d at 11-12, that squatters have no reasonable expectation of privacy. State v. Dias, 62 Haw. 52, 609 P.2d 637, 639-40 (1980). A landlord’s acquiescence to the trespass for a “considerable period of time,” however, can give rise to an expectation of privacy. Id. 609 P.2d at 640. Here, there is no evidence that the private defendants acquiesced in the Kanes’ trespass. Because the officers had probable cause to believe that a trespass was being committed in their presence, the warrantless arrest was lawful. See House, 538 P.2d at 325. As to the private defendants, even if we assume that they “initiated” the prosecution, the existence of probable cause protects them from liability as well.
b. Article I, section 7, of the Hawaii Constitution
The application of article I, section 7, of the Hawaii Constitution, is limited to criminal cases.2 State v. Okubo, 651 P.2d 494, 500 (1982), aff'd, 67 Haw. 197, 682 P.2d 79 (1984). Even if section 7 applied in a civil context, Zimmerman has not met his burden of showing that he had a legitimate expectation of privacy under Hawaii law. See Dias, 609 P.2d at 639-40. In addition, Hawaii has adopted the Matlock rule, i.e., that a third party can validate a warrantless search if they have authority to consent to search. State v. Mahone, 67 Haw. 644, 701 P.2d 171, 173-74 (1985). We agree with the district court’s dismissal of Zimmerman’s claim under Article I, section 7, of the Hawaii Constitution.
Because Zimmerman does not challenge the district court’s conclusions on the *789remaining state issues, he has waived any objections to those holdings and has abandoned those issues on appeal. See Leer v. Murphy, 844 F.2d 628, 634 (9th Cir.1988).
3. Protective Orders
Zimmerman argues that the district court erred in granting protective orders and in denying his requests for further discovery. The district court denied Zimmerman’s additional requests for discovery because “further discovery requests would be fruitless.” We conclude that neither the magistrate judge nor the district judge abused his discretion in denying Zimmerman’s discovery motions and granting defendants’ motions for protective orders.
4. Recusal
Zimmerman contends that the denial of his motions to recuse the magistrate judge and the district judge was improper. His allegations are not legally sufficient to require recusal and neither the district judge nor the magistrate judge abused his discretion in denying the motions. Zimmerman argues that the magistrate judge received a financial benefit from an investment in a city-sponsored housing development without reporting it. We decline to decide this issue because it was raised for the first time on appeal. See Brogan v. San Mateo County, 901 F.2d 762, 765 (9th Cir.1990).
5. Bifurcation of Punitive Damages Claim
Zimmerman appeals from order granting a separate trial of plaintiffs punitive damages claim and contends that separate trials are wasteful of the court’s and jury’s time. Our ruling on the other issues renders that contention moot.
6. Sanctions
In the second appeal, Zimmerman contends that the district court erred in awarding $10,006 in attorney’s fees to the private defendants pursuant to 42 U.S.C. § 1988 and Federal Rule of Civil Procedure 11.
a. Malicious Prosecution
In granting sanctions for the frivolousness of the malicious prosecution claim, the court found that there was no evidence that the private defendants controlled the decisions of the city prosecutor to initiate criminal proceedings. Contrary to the district court’s statement, there was at least some evidence to support Zimmerman’s claim that the private defendants “initiated” the proceedings. Zimmerman presented a transcript of a tape recorded conversation involving Zimmerman, Mr. Boyd, Elaine Dung Brown, and “police officer Tateishi” that could at least arguably support a finding that the desire of the private defendants to have the “proceedings initiated, expressed by direction, request or pressure of any kind” were the “determining factor in the official’s decision to commence the prosecution.” See Restatement (Second) of Torts § 653 cmt. g (1977); see also Griffiths v. CIGNA Corp., 988 F.2d 457, 463-65 (3d Cir.), cert. denied, - U.S. -, 114 S.Ct. 186, 126 L.Ed.2d 145 (1993). Although there are no Hawaii cases applying section 653, comment g of the Restatement, Zimmerman had at least an arguable basis for bringing a malicious prosecution claim against the private defendants. We conclude that the district court abused its discretion in granting sanctions on this issue.
b. Improper Motives
The district court found that many of Zimmerman’s questions “could not possibly have been designed to lead to the discovery of admissible evidence” and it concluded that Zimmerman’s “motives were to attack Bishop Estate for what it stands for.” Zimmerman argues that it was not true that he used the case to further his political campaign. A finding of improper purpose, however, is based on an objective standard. Townsend v. Holman Consulting Corp., 929 F.2d 1358, 1362 (9th Cir.1990). A court should award attorney’s fees to civil rights defendants only in exceptional cases. Mitchell v. Los Angeles Community College Dist., 861 F.2d 198, 202 (9th Cir.1988), cert. denied, 490 U.S. 1081, 109 S.Ct. 2102, 104 L.Ed.2d 663 (1989). This is such a case. On the *790basis of the district court’s examples of improper questions contained in Zimmerman’s interrogatories and requests for documents, we conclude that the district court did not abuse its discretion in imposing Rule 26(g) sanctions.3
c. Timeliness
Zimmerman also argues that the sanctions were untimely because they were awarded two years after the objectionable behavior. The appropriate time period for determining sanctionable misconduct must be evaluated in light of the circumstances of each case. See In re Yagman, 796 F.2d 1165, 1182-84 (9th Cir.), amended on other grounds, 803 F.2d 1085 (9th Cir.1986). Here, the award of sanctions was made after the order granting summary judgment to the private defendants and after denial of motions for reconsideration. We conclude that the award of sanctions was timely. Zimmerman’s additional argument that the motion for sanctions was improperly timed to intimidate him into submitting without an appeal is without merit.
d. Lack of Warning
Zimmerman argues that the sanctions were applied without any warning or caution by the court that any of his claims were frivolous. He cites no authority for the proposition that the court must give him advance warnings. Assuming that Zimmerman is making a due process argument, it is without merit. Zimmerman is entitled to notice that the court is considering sanctions against him and an opportunity to be heard in opposition. See Hudson v. Moore Business Forms, Inc., 898 F.2d 684, 686 (9th Cir.1990). The private defendants moved for imposition of sanctions and Zimmerman had an opportunity to respond. The district court held a hearing on sanctions. The district court afforded Zimmerman all the process that was necessary to safeguard his rights.
e.Amount of Sanctions
Zimmerman contends that an award of attorney’s fees of $10,006 is “high” and he claims that the court did not consider his limited resources. Although the district court should consider the plaintiffs ability to pay, see Miller v. Los Angeles County Bd. of Educ., 827 F.2d 617, 621 (9th Cir.1987), a separate hearing on the ability to pay is not required. Patton v. County of Kings, 857 F.2d 1379, 1882 (9th Cir.1988). Moreover, in Miller, the court said that a district court should not refuse to award attorney’s fees solely on the ground of the plaintiffs financial situation. Miller, 827 F.2d at 621 n. 5. Zimmerman appears to be arguing that the private defendants do not need the money, rather than arguing that he is unable to pay. The district court did not abuse its discretion in declining to consider expressly Zimmerman’s ability to pay. We conclude, however, that the district court erred by including in the sanction award the private defendants’ expenses incurred in prosecuting the Rule 11 motion. See Lockary v. Kayfetz, 974 F.2d 1166, 1178 (9th Cir.1992), cert. denied, - U.S. -, 113 S.Ct. 2397, 124 L.Ed.2d 298 (1993).
The private defendants also seek attorney’s fees and costs on appeal. Although Zimmerman did not prevail on the merits, we do not find that the appeal is frivolous and we decline to award attorney’s fees and costs on appeal.
Finally, we dismiss the city defendants from appeal No. 92-16408 because they never sought sanctions and Zimmerman does not raise any issues affecting them in this appeal.
In conclusion, we affirm the district court on the merits and the sanctions as to Zimmerman’s improper discovery motives, but reverse the sanctions regarding the frivolous*791ness of his malicious prosecution claim. We remand to the district court for recalculation of the sanctions award in accordance with this decision.
AFFIRMED IN PART, REVERSED IN PART, AND REMANDED. Each party shall bear their own costs.
. 28 U.S.C. § 1367 (1990) now codifies under the name "supplemental jurisdiction” the case-law doctrines of "pendent" and "ancillary” jurisdiction.
. Article I, section 7, provides:
The right of the people to be secure in their persons, houses, papers and effects against unreasonable searches, seizures and invasions of privacy shall not be violated; and no warrants shall issue but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched and the persons or things to be seized or the communications sought to be intercepted.
. Although the district court referred to Rule 11 sanctions, we have held that Rule 11 does not govern most discovery-related sanctions. "Sanctions for discovery abuses are governed primarily by Rule 26(g) ..., rather than Rule 11, of the Federal Rules of Civil Procedure.” In re Yagman, 796 F.2d 1165, 1187 (9th Cir.1986), see also Advisory Notes, 1983 Amendment, Fed. Rule Civ.Pro. 11 ("Although the encompassing reference to 'other papers' in ... Rule 11 literally includes discovery papers, the certification requirement in that context is governed by ... Rule 26(g).”).