The question is a red herring created to divert people's attention from fact that there is no real issue here.

There is a something in UK govermnment (and in some other countries) called the supremacy of parliament. Parliament is the supreme branch of government - it can pass any law it wants which when passed is binding with no other legal recourse. The UK has no constitution or bill of rights. The law of the land is whatever parliament says.

But this is not true of our US government - the legislative branch is not supreme. In our country the constitution is the supreme law of the land and the supreme court's intrepretation of that law is legally irrefutable. Anything Congress does is null and void if it violates the US constitution. Every officer of our country takes an oath to defend and protect the US Constitution, not the laws written by Congress which are only secondary to that, and apply only to the extent they don't contradict it.

The president is the commander in chief of all the armed forces of the United States. The framers made it crystal clear in the federalist papers and numerous other writings that any power granted in the US Constitution implies the authority to realize the intended effect of that power. They pointed out that to grant a power without granting the means to achieve it would be patently ridiculous.

The power of the president as commander in chief to intercept wartime enemy communications is irrefutable and not in question. The question comes when the foreign wartime enemy associates with agents inside our own borders, or when the communications cross our borders. Yet it would be absurd to claim that the communications of a foreign war enemy are "domestic" simply because they happen to be transmitted across or within our own borders. The content of the communication is still foreign war intelligence.

If FISA is interpreted to cover foreign intelligence then it is clearly an unlawful infringement of constitutionally granted authority - no act of congress (such as FISA) may infringe the constitution. Thus FISA covers only domestic intelligence -this is all they can cover. This is why FISA itself has already ruled that the program in question is constitutional and beyond its own authority to regulate.

Here are the transcripts from the US Dept. of Justice.
Reference: FISA Opinion
And here is a lot more background info on the entire issue: FISA briefing transcripts and other info

Or for those too lazy to read the opinion, here are two quotes:
"all the ... courts to have decided the issue held that the president did have inherent authority to conduct warrantless searches to obtain foreign intelligence information. ... We take for granted that the president does have that authority and, assuming that is so, FISA could not enroach on the president's constitutional power."
And the conclusion:
"Accordingly, we reverse the FISA court’s orders in this case to the extent they imposed conditions on the grant of the government’s applications, vacate the FISA court’s Rule 11, and remand with instructions to grant the applications as submitted and proceed henceforth in accordance with this opinion"

Any claims that this program is illegal, run contrary to FISA's own opinion of its authority. Furthermore, the Supreme Court declined to to take up the case, which implies they saw no constitutional problems.

Finally, since there are currently no allegations or evidence that the program has been abused, even if one thinks it is illegal he must still concede that it is the kind of aggressive effort we should expect the commander in chief to pursue. The executive branch's primary mission is to defend this country. It is the job of the other 2 branches to check that power when necessary. Better for the executive to err on the side of excess vigilance in their duty to protect the country, only to be checked by the other branches. That is what separation of powers and checks and balances is all about - it is how our government was intended to function.

It reminds me of my old football coach. He said he'd rather see us playing robustly and aggressively even if we get a penalty or two for interference, than to see us pussyfooting around. In this case, Bush is playing aggressively right in front of the refs yet they've ruled all the plays to be legitimate.