Fisa explained in (wikipedia)

On October 18, 2007, the House Democratic leadership put off a vote on the proposed legislation by the full chamber to avoid consideration of a Republican measure that made specific references to Osama bin Laden. At the same time, the Senate Intelligence Committee reportedly reached a compromise with the White House on a different proposal that would give telephone carriers legal immunity for any role they played in the National Security Agency's domestic eavesdropping program approved by President Bush after the Sept. 11 terrorist attacks.[51]
On November 15, 2007, the Senate Judiciary Committee voted 10–9 along party lines to send an alternative measure to the full Senate other than the one the intelligence committee had crafted with the White House. The proposal would leave to the full Senate whether or not to provide retroactive immunity to telecommunications firms that cooperated with the NSA. Judiciary Committee chairman Patrick Leahy said that granting such immunity would give the Bush administration a "blank check" to do what it wants without regard to the law. Arlen Specter of Pennsylvania, the top Republican on the committee, said that court cases may be the only way Congress can learn exactly how far outside the law the administration has gone in eavesdropping in the United States. When
the full Senate takes up the bill, Specter is expected to offer a compromise that would shield the companies from financial ruin but allow lawsuits to go forward by having the federal government stand in for the companies at trial.[52][needs update]
On the same day, the House of Representatives voted 227–189 to approve a Democratic bill that would expand court oversight of government surveillance inside the United States while denying immunity to telecom companies. House Judiciary Committee chairman John Conyers left the door open to an immunity deal in the future, but said that the White House must first give Congress access to classified documents specifying what the companies did that requires legal immunity.[53]
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In February 2008, the Senate passed the version of the new FISA that would allow telecom companies immunity. On March 13, 2008, the U.S. House of Representatives held a secret session to discuss related information. On March 14, the House voted 213–197 to approve a bill that would not grant telecom immunity – far short of the 2/3 majority required to override a Presidential veto.[54] The Senate and House bills are compared and contrasted in a June 12, 2008 report from the Congressional Research Service.[55]
On March 13, 2008, the House of Representatives held a secret, closed door meeting to debate changes to the FISA bill.[56]
Foreign Intelligence Surveillance Act of 1978 Amendments Act of 2008/w/index.php?title=Foreign_Intelligence_Surveillance_Act&action=edit&section=20
Main article: Foreign Intelligence Surveillance Act_of 1978 Amendments_Act of 2008
The 2008 amendment of FISA gave telecoms immunity, increased the time allotted for warrantless surveillance, and adds provisions for emergency eavesdropping. On June 20, 2008, the House of Representatives passed the amendment with a vote of 293 to 129.[57][58] It passed in the Senate 69 to 28 on July 9, 2008[59] after a failed attempt to strike Title II from the bill by Senator Dodd.[60] On July 10, 2008, President Bush signed it into law.
2015 USA Freedom Act/w/index.php?title=Foreign_Intelligence_Surveillance_Act&action=edit&section=21
On June 2, 2015, many provisions of the 1978 with the passage of the USA Freedom Act.[61] The 2015 law overhauled the powerful United States National Security Agency and required the US government to undergo standard court procedures in order to gather data regarding suspicious activities.[61] However, the law did not completely repeal the controversial Patriot Act and allowed some provisions to expire in later time.[61