| FOR PUBLICATION UNITED STATES COURT OF APPEALS FOR THE NINTH CIRCUIT PACIFIC FISHERIES CORPORATION, a
California corporation,
 Plaintiff-Appellant,
 No. 99-16209
 v.
 D.C. No.
 HIH CASUALTY & GENERAL                                       
            CV-97-04174-CRB
 INSURANCE, LTD.; HIH MARINE
 INSURANCE SERVICES, INC.; HARLOCK                      
            OPINION
 WILLIAMS LEMON, LTD., a
 corporation,
 Defendants-Appellees.
 Appeal from the United States District
            Court for the Northern District of California
 Charles R. Breyer, District Judge,
            Presiding
 Argued and Submitted November 15, 2000--San Francisco, California
 Filed February 9, 2001 Before: J. Clifford Wallace, Raymond
            C. Fisher, and Johnnie B. Rawlinson, Circuit Judges.
 Opinion by Judge Rawlinson _________________________________________________________________
 COUNSEL Dorothy F. Henson, Henson &
            Henson, San Francisco, Cali- fornia, for the plaintiff-appellant.
 Robert N. Windes, Le Gros, Buchanan
            & Paul, Seattle, Wash- ington, for the defendants-appellees.
 _________________________________________________________________ OPINION RAWLINSON, Circuit Judge: The Pacific Fisheries Corp. ("Fisheries")
            appeals the dis- trict court's judgment following bench
            trial and denial of
                               
            1851 Fisheries' motion for a new trial in
            its diversity action against
 HIH Casualty & General Insurance
            and HIH Marine Insur-
 ance Companies ("The Insurers").
            Fisheries alleges that the
 court erred in denying its untimely
            demand for a jury trial.
 Fisheries also contends that because
            the breach of the trading
 warranty contained in the marine insurance
            policies did not
 itself cause the loss, its losses should
            have been covered.
 Because the district court properly
            denied the untimely jury demand and correctly found that the
            insurance policies were
 voided by breach of the trading warranty,
            we affirm.
 BACKGROUND The Appellant, Fisheries, operates
            a fishing vessel called the Icy Point. The Icy Point embarked
            on a fishing excursion
 in the Pacific Ocean from San Francisco
            on February 17,
 1997. On March 11, 1997, Fisheries
            purchased insurance cov-
 erage from The Insurers under two policies:
            a Protection and
 Indemnity Policy ("P&I")
            and a Hull and Machinery Policy
 ("Hull"). Each of these policies
            contained an identical trading
 warranty which provided that Fisheries'
            insured vessel was
 confined to the Pacific Ocean and was
            not to travel beyond
 certain points of that ocean.1
 On March 31, 1997, the Icy Point
            began traveling to Guam in the normal course of business. The
            travel to Guam consti-
 tuted a breach of the trading warranty.
            While in Guam, an
 employee of the ship filed a lawsuit
            against Fisheries on the
 ground that the malfunction of the
            boat's freshwater system
 caused him to suffer dehydration. When
            Fisheries informed
 The Insurers of these events, The Insurers
            advised Fisheries
 that they needed to determine the reason
            for the ship's breach
 _________________________________________________________________
 1 The vessel was "confined to
            the waters and tributaries of the Pacific
 Ocean not west of 165 degree E. longitude,
            not south of 30 degrees S. lati-
 tude, and not north of 55 degrees N.
            latitude." This area does not include
 Guam.
                               
            1852 of the trading warranty before agreeing
            to defend against the
 employee's claim. Further, The Insurers
            told Fisheries that
 they would not extend the trading warranty
            in general, even
 if they ultimately extended the warranty
            for the limited pur-
 pose of defending against the employee's
            claim.
 The vessel departed Guam on May
            10, 1997 and proceeded north, remaining outside the trading
            warranty area. Approxi-
 mately one week later, the Icy Point
            experienced an engine
 breakdown. When Fisheries informed
            The Insurers of the
 breakdown, The Insurers refused coverage
            on the ground that
 the vessel once again was in breach
            of the trading warranty.
 Fisheries filed suit for breach
            of insurance contract in Cali- fornia Superior Court on October 22,
            1997. The Insurers
 removed the action to the district
            court for the Northern Dis-
 trict of California, based on diversity,
            on November 14, 1997.
 After Fisheries' Motion to Remand was
            denied, The Insurers
 answered Fisheries' complaint on July
            31, 1998. Fisheries
 filed a demand for a jury trial on
            August 28, 1998. Pursuant
 to Federal Rule of Civil Procedure
            38(b), Fisheries' demand
 was due on August 10, 1998.2 The district
            court denied the
 demand as untimely.
 Following a bench trial, the district
            court ruled in favor of The Insurers and entered judgment on
            April 1, 1999. The
 court found that the trading warranty
            provision was material
 to the insurance policy and that Fisheries
            had deliberately
 breached the warranty in complete disregard
            of the terms of
 the insurance contract.
 _________________________________________________________________
 2 Rule 38(b) provides in relevant part,
            "Any party may demand a trial
 by jury of any issue triable of right
            by a jury by (1) serving upon the other
 parties a demand . . . not later than
            10 days after the service of the last
 pleading directed to such issue . .
            . ." Because the answer filed by The
 Insurers on July 31, 1998 was the "last
            pleading directed to such issue,"
 Fisheries' jury demand was due within
            10 days of July 31, or August 10.
                               
            1853 Fisheries filed a motion for a new
            trial on April 12, 1999,
 which was denied on May 14, 1999. Fisheries
            filed its timely
 notice of appeal on June 11, 1999.
            We have jurisdiction pur-
 suant to 28 U.S.C. S 1291.
 Jury Demand We review the district court's denial
            of Fisheries' untimely demand for a jury trial for an abuse
            of discretion. See Ticor
 Title Ins. Co. v. Florida, 937 F.2d
            447, 451-52 (9th Cir.
 1991).
 Fisheries contends that the district
            court erred in denying its demand for a jury trial pursuant to
            Federal Rule of Civil Pro-
 cedure 39(b).3 We have held,
       The
            district court, in its discretion, may order a jury trial
            on a motion by a party who has not filed a
 timely
            demand for one. F.R. Civ. P. 39(b). That dis-
 cretion
            is narrow, however, and does not permit a
 court
            to grant relief when the failure to make a
 timely
            demand results from an oversight or inadver-
 tence.
 Lewis v. Time Inc., 710 F.2d 549,
            556-57 (9th Cir. 1983); see also Chandler Supply Co. v. GAF Corp.,
            650 F.2d 983, 987-
 88 (9th Cir. 1980).
 [1] An untimely request for a jury
            trial must be denied unless some cause beyond mere inadvertence
            is shown. See
 Mardesich v. Marciel, 538 F.2d 848,
            849 (9th Cir. 1976); see
 _________________________________________________________________
 3  Issues not demanded for trial
            by jury as provided in Rule 38 shall
 be tried
            by the court; but, notwithstanding the failure of a party
 to demand
            a jury in an action in which such a demand might have
 been
            made of right, the court in its discretion upon motion may
 order
            a trial by a jury of any or all issues.
 Fed. R. Civ. P. 39(b).                               
            1854 also Russ v. Standard Ins. Co., 120
            F.3d 988, 989-90 (9th Cir.
 1997) (holding that the district court
            could not employ
 another rule to circumvent this circuit's
            prohibition on grant-
 ing untimely jury demands due to inadvertence);
            Kletzelman
 v. Capistrano Unified Sch. Dist., 91
            F.3d 68, 71 (9th Cir.
 1996) (denying untimely jury demand
            when due to counsel's
 oversight and inadvertence); Wall v.
            Nat'l R.R. Passenger
 Corp., 718 F.2d 906, 910 (9th Cir.
            1983) (holding district
 court's denial of untimely jury demand
            not an abuse of discre-
 tion where counsel's inadvertence was
            the only reason
 shown).
 [2] Fisheries attempts to distinguish
            between inadvertence and what it characterizes as a good
            faith mistake of law.
 Apparently, counsel misinterpreted
            Federal Rule 81(c), North-
 ern District of California's local
            rules and state civil proce-
 dure rules and erroneously calculated
            the period of time
 available to make the demand. Counsel's
            reasons for his
 errors are of no consequence because
            they are still due to
 inadvertence or oversight. Therefore,
            pursuant to the prece-
 dent of this circuit, the jury demand
            was untimely.
 In Beckham v. Safeco Ins. Co. of
            Am., 691 F.2d 898, 905 (9th Cir. 1982), the plaintiff also
            attempted to excuse a late
 demand for a jury trial because her
            attorney mistakenly
 believed that no demand was necessary
            under Federal Rule
 81(c). We held, "these facts .
            . . show nothing more than inad-
 vertence and neglect. The district
            court thus did not abuse its
 discretion in refusing to order a jury
            trial." Id. As in Beckham,
 the district court in the present case
            did not abuse its discre-
 tion in denying the demand because
            counsel inadvertently
 missed the deadline. A good faith mistake
            of law is no differ-
 ent than inadvertence or oversight.
            Therefore, an untimely
 jury demand due to legal mistake does
            not broaden the district
 court's narrow discretion to grant
            the demand.4
 _________________________________________________________________
 4 Fisheries also attempted to distinguish
            this case on the basis that the
 district court judge stated he had
            no discretion to grant a jury trial. Rather,
 the judge recognized his limited discretion
            under the law of this circuit.
                               
            1855 Breach of Trading Warranty
 The district court's interpretations
            of state law are reviewed de novo. See Wetzel v. Lou Ehlers Cadillac
            Group, 222 F.3d
 643, 646 (9th Cir. 2000).5
 [3] Fisheries also argues that the
            district court erred in hold- ing that the insurance policies were
            void due to Fisheries'
 breach of the trading warranty.6 Fisheries
            contends that
 because the breach of the trading warranty
            itself did not cause
 the loss claimed, the policies are
            still effective. However,
 under California law, "breach
            of even an immaterial warranty
 will void a policy `where the policy
            expressly declares that it
 shall avoid it.' " Certain Underwriters
            at Lloyd's v. Montford,
 52 F.3d 219, 223 (9th Cir. 1995) (citations
            omitted). Causa-
 tion between the breach of warranty
            and any loss claimed is
 not required. In the present case,
            Fisheries received notice that
 any breach of the trading warranty
            would render coverage
 under the policy void. Accordingly,
            the district court did not
 err in finding the policies void.
 Motion for New Trial We review the district court's denial
            of Fisheries' motion for a new trial for an abuse of discretion.
            See DeSaracho v.
 Custom Food Mach., Inc., 206 F.3d 874,
            880 (9th Cir. 2000).
 The district court did not abuse
            its discretion in denying Fisheries' motion for a new trial.
            The court ruled that Fish-
 eries had presented no case law to
            support its contention that
 _________________________________________________________________
 5 Because this was a diversity action,
            it was governed by the law of the
 forum state. See Enron Oil Trading
            & Transp. Co. v. Walbrook Ins. Co.
 Ltd., 132 F.3d 526, 528 (9th Cir. 1997)
            (court sitting in diversity applies
 the law of the forum state).
 6 During oral arguments, counsel for
            Fisheries informed us that it was
 waiving its waiver and estoppel argument.
            Accordingly, this issue is not
 addressed.
                               
            1856 The Insurers were required to show
            that the breach of the
 trading warranty caused the alleged
            loss and, in any event, the
 terms of the warranty were material
            to The Insurers' agree-
 ment to provide insurance. Also, the
            court reiterated that Fish-
 eries had disregarded the insurance
            contract and deliberately
 breached the trading warranty.
 CONCLUSION The district court did not abuse
            its discretion by concluding that Fisheries had waived its right
            to a jury trial by failing to
 file a timely jury demand. The court's
            discretion was narrow
 because Fisheries' untimely demand
            was due to a mistake of
 law, which is no different than inadvertence
            or oversight.
 Additionally, the court did not err
            in concluding that the poli-
 cies were void due to Fisheries' breach
            of the trading war-
 ranty, regardless of the relationship
            between the breach and
 the loss. Under California marine insurance
            law, causation is
 not required and The Insurers are not
            liable for the loss. No
 abuse of discretion occurred in the
            denial of Fisheries' motion
 for a new trial.
 AFFIRMED.                               
            1857
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