President Bush on Thursday signed a sweeping revision of a 30-year-old law governing electronic spying, putting the finishing touches on one of his final legislative wins and triggering expected lawsuits from privacy advocates.

“This law protects the liberties of our citizens while maintaining the vital flow of intelligence,” Bush said at a White House signing ceremony. “This law will play a critical role in helping to prevent another attack on our soil.”

The ceremony was attended primarily by Republican lawmakers, who were virtually unanimous in their support of the legislation, in contrast with divided congressional Democrats. The House passed the bill June 20 and the Senate cleared it Wednesday.

The law would allow warrantless surveillance of foreign targets, even those communicating with people in the United States. Before that surveillance could begin, the secret FISA court would review the executive branch’s spying procedures. However, the administration could begin its surveillance before the FISA court review if it declared “exigent,” or urgent, circumstances.

What’s more, all existing lawsuits against third parties that assisted Bush’s warrantless surveillance program would be waived if a federal district court rules there was “substantial evidence” they received written assurances the program was legal and authorized by the president. A Senate Intelligence Committee report on an earlier version of the legislation detailed how the companies had received those assurances.

The dismissal of the lawsuits – which Bush has argued will ensure future private sector cooperation with government spying efforts – and enhanced authority to conduct spying were Bush’s top priorities for a rewrite of the 1978 Foreign Intelligence Surveillance Act. The bill includes some concessions to Democrats, such as the prior court reviews of surveillance procedures and whether immunity was warranted.

Civil liberties groups disagreed with Bush’s interpretation of the law, saying it violates Fourth Amendment protections against unreasonable search and seizure and prevents justified court scrutiny of the president’s surveillance program. The American Civil Liberties Union and the Electronic Frontier Foundation had both indicated they would challenge the new law in court as soon the bill is signed.