That's from a 1967 Supreme Court case called Cats.

Shortly after that, Congress enacted Title three, which governs procedures for wiretapping and electronic surveillance, in an ordinary criminal investigation.

Title three requires two things.

First, a statement of probable cause.

But in addition to that, a statement that this is probably the only way that this evidence could be obtained.

But under Title three, those requirements don't apply to national security type surveillance.

The problem is, even after Title three, the executive branch continued to engage in Elektronik surveillance of Americans based on their political opinions.

But under the guise of national security, the Foreign Intelligence Surveillance Act of 1978 or FISA, was actually intended to create more rigorous procedural requirements for this kind of surveillance.

Originally under FISA, obtaining a warrant with something like the criminal process.

The requests were individualized.

You had to show necessity, and you had to show either a foreign power or an agent of a foreign power.

Now, after a series of amendments, when it comes to a non US person overseas, you don't need any probable cause at all.

And unlike the criminal courts, FISA courts are almost completely conducted in secret title.

Three wiretaps in ordinary criminal cases air generally difficult to obtain, especially when compared to the low standard and secrecy in the FISA courts.