I have seen this a lot on social media recently: Underwear that shows the 4th Amendment when scanned at an airport. According to the company selling it, it uses metallic ink. They also claim that the words show up in x-rays.
While amusing, this is a scam.
There were several products purporting to do this 8 years ago, when scanners were first introduced. However, it is now obsolete as there is now just an avatar shown to TSA. So this shirt might show up as an anomaly on the chest, leading to a pat-down. But, chances are, an agent will never see the text of the 4th Amendment.
(Furthermore, the scanners are also now using millimeter-wave technology, not x-rays. So, while the metallic text may still be detected by the scanner, I wouldn't trust the manufacturer's word on this.They are clearly ignorant of TSA policy.)
Buy this product if you like the subversive nature of it and don't mind pat-downs. But, if you want to educate the TSA, you'd be better off handing them a pocket-sized Constitution.