The work of the court is shrouded in secrecy. Founded in 1978, the so-called FISA Court was tasked with processing government requests for surveillance against foreign targets. It was this court that approved a number of controversial programs, such as PRISM and the phone records collection program, which were later leaked by whistleblower Edward Snowden to journalists.
Because the court only hears the government's case, that's led to accusations that there aren't enough checks and balances and that it's a "kangaroo court with a rubber stamp."
Since 1979 through to 2015, the last round of reporting figures, the court has approved 38,365 warrants but only rejected a dozen. That's a rejection rate of 0.031 percent.
But only in recent years has there been a push back against the government's one-sided authority.
Last year, the court appointed five lawyers and attorneys with national security clearance -- including Marc Zwillinger, a lawyer who's represented both Apple and Yahoo at the court -- to act as pushback against the government's requests.