Washington ? With remarkable speed and near unanimity, Congress on Thursday passed legislation intended to ensure consumers can block many unwanted telemarketing calls. But whether the service millions of Americans signed up for takes effect next week was thrown into doubt when a second federal judge ruled the list violates free speech protections.

U.S. District Judge Edward W. Nottingham in Denver blocked the list late Thursday, handing another victory to telemarketers who argue the national registry is unconstitutional and will devastate their industry.

His decision came shortly after the House and Senate voted overwhelmingly for a bill making clear that the Federal Trade Commission has the power to enforce the “do-not-call” list. The legislation was prompted by an earlier ruling by a federal judge in Oklahoma City who said the FTC lacked the power to create and operate the registry.

The House voted 412-8 and the Senate 95-0 for the bill. President Bush said he looked forward to signing it. “Unwanted telemarketing calls are intrusive, annoying and all too common,” he said in a statement.

The list that would block an estimated 80 percent of telemarketing calls is supposed to be effective Wednesday, but it’s unclear whether legal issues will be settled by then. Even after Bush signs the legislation, the FTC must win in court for the list to move forward.

Despite the uncertainty, the FTC is encouraging people to continue signing up for the list at the Web site www.donotcall.gov or by calling (888) 382-1222.