WASHINGTON ( CNN ) -- Steve Bierfeldt says the Transportation Security Administration pulled him aside for extra questioning in March . He was carrying a pocket edition of the U.S. Constitution and an iPhone capable of making audio recordings . And he used them . Steve Bierfeldt is accusing the Transportation Security Administration of `` harassing interrogation . '' On a recording a TSA agent can be heard berating Bierfeldt . One sample : `` You want to play smartass , and I 'm not going to play your f**king game . '' Bierfeldt is director of development for the Campaign for Liberty , an outgrowth of the Ron Paul presidential campaign . He was returning from a regional conference March 29 when TSA screeners at Lambert-St. Louis ( Missouri ) International Airport saw a metal cash box in his carry-on bag . Inside was more than $ 4,700 dollars in cash -- proceeds from the sale of political merchandise like T-shirts and books . There are no restrictions on carrying large sums of cash on flights within the United States , but the TSA allegedly took Bierfeldt to a windowless room and , along with other law enforcement agencies , questioned him for almost half an hour about the money . The American Civil Liberties Union has taken up Bierfeldt 's cause and is suing Secretary of Homeland Security Janet Napolitano , whose department includes the TSA . Their complaint alleges that Bierfeldt was `` subjected to harassing interrogation , and unlawfully detained . '' Larry Schwartztol of the ACLU said the TSA is suffering from mission creep . `` We think what happened to Mr. Bierfeldt is a reflection that TSA believes passenger screening is an opportunity to engage in freewheeling law enforcement investigations that have no link to flight safety , '' he said . Schwartztol believes many other passengers have been subjected to the same kind of treatment , which he claims violates constitutional protections against unlawful searches . The TSA would n't comment on the lawsuit , but said in a statement that the movement of large amounts of cash through a checkpoint may be investigated `` if suspicious activity is suspected . '' Unbeknownst to the TSA agents , Bierfieldt had activated the record application on his phone and slipped it into his pocket . It captured the entire conversation . An excerpt : . Officer : Why do you have this money ? That 's the question , that 's the major question . Bierfeldt : Yes , sir , and I 'm asking whether I 'm legally required to answer that question . Officer : Answer that question first , why do you have this money . Bierfeldt : Am I legally required to answer that question ? Officer : So you refuse to answer that question ? Bierfeldt : No , sir , I am not refusing . Officer : Well , you 're not answering . Bierfeldt : I 'm simply asking my rights under the law . The officers can be heard saying they will involve the Federal Bureau of Investigation and the Drug Enforcement Administration , and appear to threaten arrest , saying they are going to transport Bierfeldt to the local police station , in handcuffs if necessary . Bierfeldt told CNN he believes their behavior was inappropriate . `` You 're in a locked room with no windows . You 've got TSA agent . You 've got police officers with loaded guns . They 're in your face . A few of them were swearing at me . '' But the officers did not follow through on their threats . Near the end of the recording an additional officer enters the situation and realizes the origins of the money . Officer : So these are campaign contributions for Ron Paul ? Bierfeldt : Yes , sir . Officer : You 're free to go . According to the TSA , `` Passengers are required to cooperate with the screening process . Cooperation may involve answering questions about their property . A passenger who refuses to answer questions may be referred to appropriate authorities for further inquiry '' Bierfeldt contends he never refused to answer a question , he only sought to clarify his constitutional rights . `` I asked them , 'Am I required by law to tell you what you 're asking me ? Am I required to tell you where I am working ? Am I required to tell you how I got the cash ? Nothing I 've done is suspicious . I 'm not breaking any laws . I just want to go to my flight . Please advise me as to my rights . ' And they did n't . '' The TSA says disciplinary action has been taken against one of its employees for inappropriate tone and language .
Passenger questioned about large amount of cash . He says the money was from sale of political merchandise . ACLU is suing Homeland Security Secretary on behalf of passenger . TSA says movement of large sums of cash may be investigated .