"Where does this stop?"

I picked this up via Eschaton, from Glenn Greenwald, who notes that there was a proposal to lower the standard of FISA to "reasonable suspicion." One reason Congress didn't make that amendment to the statutes was because the Bush Administration opposed it. One reason the Bush Administration proposed it was because it might be unconstitutional:

The Department's Office of Legal Counsel is analyzing relevant Supreme Court precedent to determine whether a "reasonable suspicion" standard for electronic surveillance and physical searches would, in the FISA context, pass constitutional muster. The issue is not clear cut, and the review process must be thorough because of what is at stake, namely, our ability to conduct investigations that are vital to protecting national security. If we err in our analysis and courts were ultimately to find a "reasonable suspicion" standard unconstitutional, we could potentially put at risk ongoing investigations and prosecutions.

This is the fundamental issue that we simply cannot talk around: once you start pulling at the threads of the basic legal fabric of the country, the whole thing unravels quite rapidly.

So Gen. Hayden's statement that the standard in the 4th Amendment is "reasonable suspicion" is not just a simple error: it tugs at the tapestry of our entire legal system and, if put into practice, might undo much more than they bargained for.

The President simply cannot use his Constitutionally created office to undo provisions of the Constitution, without undoing the Constitution itself. And even his Department of Justice understands that.

But apparently Alberto Gonzalez doesn't.