The U.S. law allowing the importation of grey-market cars that are 25 years old or older will stand. A petition to get the government to shorten the waiting period to 15 years failed to attract the necessary 25,000 signatures.
The petition, set up on Whitehouse.gov's We the People petition site, asked the Obama administration to "Stop using Homeland Security funds to seize imported vehicles, and change the DOT/EPA exemption to 15 years." If the petition had met the minimum quota of signatures, White House staff would have reviewed it, "sent [it] to the appropriate policy experts, and [issued] an official response."
Instead, supporters are back to the drawing board. They'll have to come up with another way to push an effort to get the U.S. law to harmonize with a similar law in Canada law, which allows grey-market cars 15-years-old or older to be registered in that country for citizens' use.
They can always fall back on traditional means of civil disobedience, like occupying the DOT with a Keicar drum circle.
(Thanks to e.pie and Matthew for the tip)