Crispin Porter + Bogusky and its largest client, Burger King, are asking a federal judge to determine if their campaign for BK’s Chicken Fries violates trademark protection of heavy-metal band Slipknot. The Aug. 12 filing by the Miami shop was in response to a letter the agency and restaurant chain received earlier in the month demanding that they remove television commercials or face legal action. The band has accused CP+B and BK of mimicking its live performances. TV commercials and a Web site, www.coqroq.com, feature a mock band called Coq Roq whose members wear masks, as do members of Slipknot. The threat of litigation from Slipknot is hindering the company’s ability to continue developing the campaign, the company said in court documents. CP+B and BK declined to comment.