The Alaska Republican is scheduled to go on trial next month on charges that he lied on Senate disclosure records about hundreds of thousands of dollars in gifts and services he received from a powerful oil services contractor, VECO Corp.
Stevens said the FBI intruded on his Senate affairs when it questioned members of his legislative staff. He cited the Constitution's speech-or-debate clause, which prohibits the executive branch from using its law enforcement authority to interfere with legislative business.
He also argued that it's up to the Senate, not the Justice Department, to enforce Senate rules about financial disclosure. If the Senate feels he violated its rules, it can punish him, he said.
The Senate's longest-serving Republican, Stevens has been a political force in Alaska since before it became a state. He has been dogged by the corruption case and now faces a challenge in the Republican primary.
He asked for an unusually speedy trial that he hopes will clear his name in time for the November election.
VECO employees normally build oil drilling and processing equipment. But VECO workers led the renovation of the senator's home, a project that was overseen by company founder and longtime Stevens friend Bill Allen. Stevens says he paid every bill he received.
Prosecutors say he got hundreds of thousands of dollars in freebies and discounted work that Stevens should have disclosed.
Stevens' attorneys argued Thursday that prosecutors were trying to insinuate bribery without actually charging it. They asked a judge not to let jurors see a paragraph in the indictment about those official actions.
"This language is blatantly inflammatory and prejudicial," attorneys wrote.
The Justice Department was due to file its own documents late Thursday.