The Competitive Enterprise Institute (CEI), a libertarian think tank, is suing the TSA for “failing to follow basic required administrative procedures” before using invasive body scanners on passengers.

The suit accuses the agency of neglecting their duty to publish rules and regulations for scanner use and open them up to public comment and judicial review.

In a press release, CEI noted that, “As of today, the TSA has still not issued a final rule on body scanners. At the same time, TSA has greatly expanded its use of body scanners, even as doubts over their effectiveness grow.” According to their lawsuit, the agency has already installed over 740 scanners at 160 airports.

"For four years the TSA has flouted the court's order, preventing the public and outside experts from scrutinizing their actions as required under the law," CEI research fellow and co-petitioner Marc Scribner told USA Today. "This lawsuit aims to enforce that court decision and bring much needed accountability to an agency plagued by lawlessness."

CEI is joined in the suit by the National Center for Transgender Equality (NCTE) and the Rutherford Institute.

The transgender group wrote that they have "a special interest in this issue because transgender travelers commonly report experiencing additional scrutiny at airports." According to NCTE, between 2008 and 2009, 21 percent of transgender people reported that they were harassed at an airport.