Taken from [url]
http://www.usatoday.com/news/nweird/nweird.htm[/url]

LUDINGTON, Mich. — Since 1947, Henry Marek has kept a World War I-era cannon in his front yard. Over the years it has become a Mason County landmark But a Defense Department worker happened to notice the cannon last week, knocked on Marek's door and told him that the cannon is government property. That means it could be seized and destroyed. That's when Marek brought out his heavy gun — U.S. Rep. Pete Hoekstra, who has ridiculed the government's sudden interest in the weaponry. "At a time when the Defense Department is fighting a war against terrorism, it seems strange they would want to fight Mr. Marek over an 80-plus-year-old cannon that was long-ago disabled," he said.

They don't need a law.  They decide on the law as they go along.  It is for your own good.