I don't support the Assault Weapons Ban, but the place to beat it is in Congress.
But it is not unConstitutional. It is an abomination and a hassle, and it will expire. That Bush would extend it is simply due to his ethical habit of keeping his campaign promises, of which one was to support existing gun laws and to fight all new gun control laws.
Prescription drug coverage can be Constitutional (no one denies that the government has a right to supply our soldiers in the field with battlefied medicine, for instance), and it can also be Conservative (see previous battlefield example). So the devil is in the details.
Nationalizing the entire healthcare industry wouldn't be Conservative, but that's something that a Gore, Kennedy, or a Clinton would do, not a Bush.
With Bush, you'll get a little political jujitsu that will yield reasonable Prescription Drug coverage, denying the "issue" to Democrats, but that won't nationalize our doctors, a deft combination that critics of Bush still can't comprehend.