@ErikUden stuff like this from back in the day. People made them as a protest of the anti-circumvention provisions of the DMCA. https://www.ebay.com/itm/134064494841

That shirt contains the (perl, I think) source code required to break the "css" encryption on DVDs. Because css is a "technological protection measure" and that code defeats it, the code, and arguably the t-shirt, is an illegal "circumvention device" under the DMCA.