Sorry your wrong. Take a look at the links I posted to you. Not all searches require a warrant. Never have, never will. I'm not a constitutional lawyer, but I've had enough con law courses over the years to know the parameters of the 4th amendment in this area. The government may make reasonable searches at reasonable times. Getting a warrant essentially guarantees (even though the defense can argue it wasn't reasonable or the details weren't correct, etc. and sometimes win)that the grounds are reasonable so it doesn't have to be completely litigated during trial.
In terms of electronic surveillance FISA has defined the search of US persons (not just US citizens) to require a warrant with exceptions. Read the act for the exceptions. However, Congress can not limit the inherent powers of another branch of government unless the right to limit it is in the Constitution. For example congress can limit what areas courts have authority over or specify areas or cases that the courts can't deal with.
There are several issues with the current case. The first is the inherent power of the president as Commander in Chief and the presidents sole authority in foreign affairs except for the advice and consent provisions for treaties. Congress' control is through the purse. In addition to the inherent powers of the president in both those areas Congress through the joint act that they passed after 9/11 gave the president even broader powers (read the act). A lot of those powers are explicit in the act but even more powers are implicit in the act.
The second issue is the listening that they were doing on international calls from and to known Al Quada operatives and agents to US Persons reasonable under the conditions that existed at the time. To and from non US Persons no warrant is required by FISA (it's in the act).
In addition to be covered by the FISA act the calls have to be intercepted within the United States (per the act). If they were intercepted in the UK, Australia and several other countries where we have major facilities no warrant is required per FISA since it only applies to calls intercepted within the US.
The president has a pretty strong legal position in my and many constitutional lawyers opinions in spite of what the media might say. The weakest one is the reasonableness argument. That's a matter of opinion and there are lots of shades of gray. What's reasonable depends on the situation at the time it occurs. In a war against a stateless enemy who operates world wide what's reasonable hasn't been defined.
You've gone far afield from this comment that I responded to:
The 4th amendment protects against unreasonable search and seizure. The issue is what's reasonable and unreasonable. Those change with the situation just like what's free speech. You can't yell fire in a crowded theater. You can search a building for someone if you're in hot pursuit without a warrant when under ordinary circumstances it would require a warrant. Your luggage can be opened and inspected by customs without a warrant when you are entering or leaving the country. Your vehicle can be searched when entering and leaving the building. If you're driving across the country they can't search your luggage or car without a warrant (with exceptions)
Unreasonable means no warrant. Reasonable means that they get a warrant and had better be able to back it up.
BTW, you can yell fire in a theater. In fact, there are times that you should. If there happens not to be a fire, then that is a different issue. That's a misuse of your right to free speech and you can be charged.
Exigent circumstances do allow police to enter a building if they hear a cry for help or are chasing a suspect and he just entered the building. That searching would not include anyplace that a person could not hide in. But neither of these situations are what we are discussing.
Forget your lawbooks for a minute. I've acknowledged that the 'law' might say something different. I'm asking you to read the 4th carefully. My reading doesn't require that you torture or twist the words. The Founders intended that the government jump through hoops to search you or your effects -- even in scary times. If you want to change that, amend the Constitution.