25 year Vehicle Import law to 15 years

In the 1980s, there was a law/ban made to stop personal imported cars or Grey Market cars into the US.In result to this, nobody could import any car that was 24 years or younger.Us car enthusiasts think it was Mercedes and BMW that spent millions trying to get this law passed by congress.Why does the United States have a 25 year law, when just up north, Canada has has a 15 year law.I think we should revise the law and being it down to 15 years instead of 25.