Members of the group Rush, from left, Alex Lifeson, Geddy Lee and Neil Peart, are shown in an undated photo. (Canadian Press)

Canadian rock band Rush has sent a letter to Kentucky U.S. Senate candidate Rand Paul, saying his campaign is violating copyright laws by playing Rush music without permission.

The Courier-Journal of Louisville reported that Rush's attorney, Robert Farmer of Toronto, sent the letter to the Paul campaign, asking the would-be senator to stop using the music.

"This is not a political issue — this is a copyright issue," Farmer told the newspaper. "We would do this no matter who it is."

Paul's campaign used Rush's The Spirit of Radio to energize a rally and another song, Tom Sawyer, in a fundraising video.

Paul also has used a line from The Spirit of Radio in speeches: "Glittering prizes and endless compromises shatter the illusion of integrity."

Paul is a Republican candidate with significant support from the Tea Party movement.

His campaign manager Jesse Benton said Wednesday that he had received the letter, but called it a non-issue.

"The background music Dr. Paul has played at events is a non-issue," Benton told USA Today. "The issues that matter in this campaign are cutting out-of-control deficits, repealing Obama Care and opposing cap-and-trade."

Rush, a rock band with Geddy Lee as lead vocalist, Alex Lifeson on guitar and drummer Neil Peart, is remarkable for its longevity. A recent documentary, Rush: Beyond the Lighted Stage, examined the legacy of the band, which formed in Toronto in 1968.