The 2004 expiration of the 1994 "assault weapon ban" is part of the "existing gun laws".
No one's faulting Bush for enforcing the present ten-year ban, they're faulting him for saying that he would enact a *NEW* ban (presumably a permanent one) when the old one expires.
Rove is either an idiot, or a bad bald-faced liar, and neither option inspires confidence.
I admit to being very ignorant on gun laws, so can you give me a link where Bush wants to enact a 'new' one?