The alternative is what we had before FISA, right? The government can snoop for foreign intelligence, and does not need a warrant to do so. FISA was passed so evidence uncovered while snooping for foreign intelligence could be used to prosecute criminal activity. The Keith case is what triggered FISA - was a prosecution of a bomber operating in the US. The government didn't bother to get a warrant, and argued it didn't need one.
When the case is REALLY spying, no warrant is needed, period. Aldrich Ames house was tossed, no warrant, no issue either. How the F.B.I. Finally Caught Aldrich Ames. Post-FISA, for what it's worth.
-- There needs to be strict controls on that ... --
LOL. FISA has "strict controls," and the real upshot of FISA is a make work to the order of millions of dollars worth of lawyers and judges. Stacks of paper nobody will ever refer to. Total waste. Shut it down.
The government is always going to snoop on its citizens to the extent technology facilitates. The law has no effect against the government.
FIXED!