FISA....

Read what it is and why it exists. But there are some interesting pieces like this...

"[A]gencies are not authorized to use such techniques as electronic surveillance, unconsented physical searches, mail surveillance, physical surveillance, or monitoring devices unless they are in accordance with procedures established by the head of the agency concerned and approved by the Attorney General." EO 12,333, para. 2.4. Dep't. of Defense (DOD) Directive 5240.1-R implements FISA and EO 12,333 within DOD. These authorities govern the collection of intelligence by the U.S. government against United States persons, whether they are located within the United States or outside the United States.

FISA does not regulate the use of electronic surveillance outside of the United States. For instance, electronic surveillance of electronic communications like e-mail is only governed by 1801(f)(4) if the surveillance device is installed "in the United States." When e-mail sent by a U.S. person to a foreign person is intercepted outside the United States, that interception does not meet this definition.

Generally, the law does not allow evidence collected against individuals in the US to be used against them without FISA court approval. But in reality, the recently revealed surveillance is not designed to produce evidence to convict, but evidence enough to uncover plots or to neutralize potential threats against US interests. FISA originally came about since Nixon used domestic surveillance to gather data on foes under the guise of national security. FISA provides an oversight for those activities inside the US where the ultimate goal is to prosecute.