The question over the warrantless wiretaps comes down to this:
In wartime, does the Presidency have powers that supersede Congress's laws?
Many people haven't focused on this yet - bogged down in either this one specific question of the wiretaps while ignoring the several other instances of Bush claiming this right (see the McCain amendment signing), or arguing the minutiae of that particular Congressional act, or arguing that other people did other things like that (see Lincoln, FDR).
For the record, yes, other Presidents have done acts that were illegal at the time. Lincoln did suspend habeas corpus, when the Constitution says only Congress can do this. FDR rounded up people of Japanese ancestry and had them imprisoned in violation of several laws, and declared what could be called rigged military tribunals would be the court of choice in one case as well. Was there a difference between those acts and Bush's? As of now, one - both acts happened in an actual, declared war. Also, Congress approved Lincoln's appropriation of their power in 1863, and one of FDR's powers (military tribunals) in one particular case was affirmed by the Supreme Court in Ex Parte Quirin (which has been called badly decided by some judges and commentators), so the President's act in questions were given kind of ex post facto justification. Of course, this may happen in the current wiretap case as well.
In this case, the Congressional Research Service has found that Bush's justifications for the wiretaps don't match with current law, and that Bush didn't fully inform Congress as required. In other words, there seems to be no questions that barring any new findings, Bush did violate the law in the wiretapping, regardless of what other Presidents did or what they claim the Congressional act allowed or etc. - and we can safely ignore the Justice Department's findings, unless "conflict of interest" has been redefined.
So the question now is: Can the President assert supra-legal powers in wartime?
The past has shown he can. In both most often mentioned cases, the Presidents did trample the Constitution, and were not impeached for it. In both cases, they received after-the-fact approval and power (for FDR, in that one case only as far as I know). However, the past is not the straitjacket of the present.
If Bush were to decide that every American should be wiretapped on the chance they would come in contact with a terrorist, that would possibly be within his power during wartime and possibly would be less egregious than some of Lincoln's acts. Yet that wouldn't make it justified. There is a dividing line between the necessary and the overreach.
In this particular case, Bush went around a historically loose court, the FISA, to allow warrants with a less stringent standard. In the words of General Hayden recently, a "reasonable basis to believe" vs. "probable cause". Probable cause is roughly defined to be "good reason to believe that the search will turn up evidence of crime." And FISA gives much leeway to the agent requesting the warrant, not to mention the 72 hour allowance before even applying for a warrant. This doesn't seem to be a very tough case to make.
But let's say it is. For whatever reason, these standards are too onerous in the undeclared war on terrorism. Will this allow the warrantless wiretaps?
At first, maybe. Given the complaints from the FBI that the tips gained were worthless, and taking into consideration that the pre-9/11 problem was not too little information but too little comprehension of too much information, I will not grant an absolute yes here. But let's say maybe it was enough - at first. But going on five years since?
At some point, you have to ask if this was such a problem, why was there no effort to change the requirements needed for a FISA warrant? There have been some debates that Congress can't pass a law allowing a lower standard than "probable cause" as per the 4th Amendment, but there could have been allowances for, say, longer notification times or more deference to the requesting agent. There were workarounds. Yet the Bush Admin. made no effort to make any workarounds.
So Bush found the already loose requirements of the FISA too strict and authorized warrantless taps, never tried to fix the supposed underlying problems with the requirements, never authorized Congress as required by law, and even when they knew the New York Times had the story for over a year before printing it made no effort to change the law even then. These are not the actions of a President who feels that some law as written isn't sufficient for needed protection and can be amended later; these are the actions of a President who feels that some law as written simply doesn't apply to him at all and therefore needs no amending or changing.
The same could be said of FDR and Lincoln, but they eventually did receive some allowances from the courts or Congress in their action. I do not know if the current Congress will be so understanding, and I am not sure I would want them to be. In my case, it comes down to trust, and I don't trust Bush with this power, given his signing amendment in the McCain anti-torture act and others. I also include in my thinking the recent ACLU lawsuit alleging that Christopher Hitchens, among many others, were targeted by warrantless wiretaps.
And my final reason to deny this power to Bush - to allow him to skip warrants - is this:
We are in a war where almost any means could be justified for the amorphous idea of "protection". Camps for people following Islam, taps on all international calls, taps on all calls domestically that may include trigger words, data sieves on all Internet accounts...you can think of many things that could help. This does not mean they should be done, or need to be done. There is a balance, and I don't feel the Bush Admin - nor any future ones - can place this act on the seesaw without overbalancing away from privacy rights and into a police state. After all, a reasonable basis to believe depends on some person's reason, and in an era of fear, reason can be very unbalanced.