A dispute over ad revenue may lead to the end of Rush Limbaugh's relationship with Cumulus Media. Reuters

First Rush Limbaugh was dropped by his advertisers. Now, he's been dropped by the rock band Rush, after the band of his namesake formally demanded that the conservative radio host stop using their music on air following incendiary comments he made about a female Georgetown law student.

The Canadian rock band -- famous for a series of 1980s hits including Tom Sawyer and Fly By Night -- sent the shock-jock a cease and desist letter via their attorney on Tuesday, according to radio host and author Bob Cesca, who received a copy of the letter.

Limbaugh has been playing Rush music for years as bumper music out commercial breaks on his radio program. In fact, Cesca pointed out that Limbaugh was playing the Rush track The Spirit of the Radio last week as he made misogynistic comments about Sandra Fluke, the law student who attracted national attention after she was denied the ability to testify in a congressional hearing about the Obama administration's contraception mandate that was led by House Oversight Committee Chair Darell Issa, R-Calif.

The Rush song was reportedly playing in the background when Limbaugh argued that Fluke, as well as other women who believe contraception should be fully covered by health insurance plans, should post videos of themselves having sex online if she wants to be paid to have sex.

Cease and Desist Letter

In the official cease and desist letter Bob Farmer, the head of legal affairs for Rush's management company S.R.O. Management Inc., their music publishing company Core Music Publishing and their record company The Anthem Entertaining Group Inc., wrote the band did not want their music associated with what is essentially a political broadcast.

The use of Rush's music in this manner implies an endorsement of the views expressed and products advertised on the show, and is in breach of not only copyright and trademark rights, but also, of section 51 of the New York Civil Rights Law, the letter states.

Limbaugh has been targeted by Democrats, women's groups and a variety of pundits after he called Fluke a slut and a prostitute last week for campaigning Georgetown University to include birth control coverage in employee health insurance plans.

Although the event was far from the first time Limbaugh has made egregiously inappropriate comments on his show, this time the consequences were immediate. As of Thursday, 42 advertisers and two radio stations distanced themselves from The Rush Limbaugh Show.

Despite the public outcry, Limbaugh doesn't seem to be worried. On Wednesday he told his listeners that everything's cool and noted that many of the advertisers who yanked their support were local and as a result, will have little impact on the show's revenues.

[The advertisers] are not canceling the business on our stations. They're just saying they don't want their spots to appear in my show. We don't get any revenue from 'em anyway. The whole effort is to dispirit you, Limbaugh said.

Limbaugh estimated that as many as 18,000 companies could be advertising on any of the approximately 600 stations that broadcast his radio program, which airs for three hours on weekdays.