So it's your position that the President is not bound by any law? That's a tough one to argue, imo. But, since the constitution itself requires a warrant, not FISA, the law does not limit the President. It actually ENABLES him to get warrants, but secretly. It does not limit his powers.
The constitution doesn't require a warrant. It requires reasonableness. Read it. It says "The right of the people to be secure...against unreasonable searches and seizures shall not be violated". It doesn't say searches without warrants are forbidden. It says warrants without probable cause and particularity are forbidden.