If there's a zombie apocalypse, we're all screwed.
Why? The first amendment to the U.S. Constitution. See, since it's ratification in 1787, several countries inside and outside of North America have adopted many ideas in the Constitution, especially the first amendment made to it in the Bill of Rights. In this, it says that the people have a right to peaceful assembly. I hate to admit it, but zombies are technically people. So if anyone is ever on the top of a car facing off against a horde of undead, he is not allowed to fire into the crowd that, up until they bite him, are merely trying to get up to him to speak in private.
Also, the third amendment prevents soldiers returning to Iraq from sleeping, eating, or residing in any way, shape, or form in their own homes.