ROCKVILLE, Md.—Videogame designers at ZeniMax Media Inc.'s Bethesda Softworks destroyed a virtual U.S. Capitol, Jefferson Memorial and other landmarks in the Mature-rated "Fallout 3," which depicts the ruins of post-apocalyptic Washington.

They didn't bother to obliterate the U.S. Supreme Court. But in the real world, that's where the $10.5 billion videogame industry faces its greatest threat. On Tuesday, the court's nine justices will consider whether to strip First Amendment protection from violent videogames...