More than 300 years ago, British warships clashed with Spanish vessels off the coast of present-day Colombia, sending to the bottom of the sea a galleon that’s now believed to hold billions of dollars in treasure.

Sea Search Armada, an ocean salvage company based in Bellevue, Wash., has long been locked in a fight with the Republic of Colombia over claims to the sunken treasure, which remains unrecovered at a depth of about 1,000 feet. The legal effort hit another snag on Monday, when the U.S. Court of Appeals for the D.C. Circuit upheld a trial judge’s ruling dismissing the company’s suit.