No argument at all really, since the diver had no title to the silver, because the silver remained property of the U.S. Navy. It was not declared surplus, and was not a war trophy.

As I understand it, ship's silver is a controlled item and must be inventoried annually. When a ship is decommissioned, the ship's silver is returned to the Navy Yard for storage.

Unfortunately, the author of the article is wrong when he says:

The silver is not unlike most other relics brought home by veterans.

The silver is very different from your grandfather's uniform, captured Luger or Samurai sword. It was not declared surplus, and was not a war trophy. The diver recovered it it from USN property while on duty in a official capacity.

The author makes a specious argument that the "the silver from the Arizona was salvaged by a diver during the War, long before the sunken ship was declared a national cemetery or a memorial. The USS Arizona became a war grave on December 7, 1941, not when declared by President Eisenhower in the 1950's. Those that died aboard her did not disappear that day and magically reappear when declared a memorial.

The Arizona was stricken from the Navy Registry in 1942, but was not sold for scrap, transferred to another government, nor was it donated as a museum ship. It remained government property. The ship's silver was not the personal property of a sailor, but a controlled item of the Arizona.

So, for all of his wailing and gnashing of teeth, the author of the linked article is off-base when he claims that the Navy should have bid on the set.