Don Imus, the tousled and acerbic radio host whose racial remarks engendered a media storm that triggered a swift upending of his career, is not going away quietly even if the imbroglio has all but disappeared from the national conversation in the wake of the Virginia Tech massacre.

For Imus, who made a career out of operating in the murky space between sophomoric humor and high-brow political talk, there is the little matter of about $40 million left on his contract with CBS Radio - whose boss Les Moonves fired the shock jock on April 12. CBS' lawyers contend Imus was fired for cause and not owed the rest of the money.

But Imus has hired one of the nation's premiere First Amendment attorneys, and the two sides are gearing up for a legal showdown that could turn on how language in his contract that encouraged the radio host to be irreverent and engage in character attacks is interpreted, according to one person who has read the contract.

The language, according to this source, was part of a five-year contract that went into effect in 2006 and that paid Imus close to $10 million a year. It stipulates that Imus be given a warning before being fired for doing what he made a career out of making off-color jokes. The source described it as a "dog has one- bite clause." A lawsuit could be filed within a month, this person predicted.

But in Imus' case, his free speech rights are tempered by the fact that he said what he said on the public airwaves - which are subject to Federal Communications Commission regulations about what is appropriate content.