A bill to expand the government’s ability to eavesdrop on Americans appears to be headed for passage in the Senate this week. This is a mistake.

The bill, said by the Bush administration to be necessary to protect the country from terrorist attacks, would weaken the Foreign Intelligence Surveillance Act. The act, enacted in 1978 in the wake of Watergate, requires the government to get a warrant to listen in on communications between Americans and those in another country. A secret court considers the warrant requests. Since 1978, the FISA court has approved nearly 20,000 warrants and rejected fewer than 10.

This does not appear to be a high hurdle, yet the Bush administration first went around it secretly and then pressured Congress to formalize what the administration was already doing. After the Sept. 11 terrorist attacks, the White House had the National Security Agency eavesdrop on phone calls and e-mails between the United States and other countries without warrants. When this was revealed by press reports in 2005, the Bush administration sought congressional permission to continue the electronic monitoring with as little oversight as possible. It also has long sought immunity from lawsuits for the communications companies that participated in the eavesdropping.

Days before its 2007 summer recess, Congress passed the Protect America Act, which allowed monitoring of electronic communications by people in the United States without a court’s order or oversight, so long as the target of such monitoring was “reasonably believed” to be outside the U.S. Surveillance could be authorized by the director of national intelligence and the attorney general, with the FISA court relegated to examining whether the government’s guidelines for targeting overseas suspects were appropriate.

This act expired earlier this year despite warnings from the White House that not extending it would make the country vulnerable to terrorist attacks. Now, lawmakers are again under pressure to loosen the FISA requirements and to grant immunity from lawsuits to the communications companies that participated in the NSA program.

There is a better way. An amendment, sponsored by Sen. Jeff Bingaman, a New Mexico Democrat, and co-sponsored by Republican Sen. Arlen Specter, the ranking member of the Judiciary Committee, would delay a decision on immunity (while putting current lawsuits on hold) until after the release of an inspector general’s report on the NSA spying program.

This would give lawmakers a sense of what the spying program entailed. Today, few of them know what the telecom companies and the government did. Granting immunity from lawsuits before knowing this makes no sense.

Reps. Tom Allen and Mike Michaud voted against the House FISA bill largely due to concerns about granting immunity. Sens. Susan Collins and Olympia Snowe have supported immunity.

An inspector general’s report could also help lawmakers know what, if any, changes are needed to the FISA law. Making changes, such as allowing the approval of bulk, rather than individual warrants, and allowing eavesdropping without court approval under loosely defined “exigent circumstances,” is premature without knowing that current legal protections are in fact a burden.