Re: To remove DRM, you'll need the open-source library, libdvdcss
The T-shirts that were considered munitions were the PGP-in-perl shirts in the early 90s, the DeCSS kerfuffle was late '90s and early '00s.
I wore the PGP-in-perl T-shirt out of and back into the USA on maybe a dozen flights from '91 to '93 without anybody even blinking at me funny. Later, I occasionally carried a copy of Bruce Schneier's "Applied Cryptography" book containing source examples in the text (which did not fall under the export restrictions) and the disk containing the very same source, which was bound into the cover (and very definitely did fall under those restrictions).
This kind of security theater may be worth the paper it is printed on, but not much more.
I stopped trying to get arrested on principle when I grew up after having a kid of my own to take care of. Priorities & all that. Today, she tells me I shouldn't have wimped out ... but she did wear the shirt and took the book into "show and tell" occasionally, as examples of governmental stupidity.
My Grand daughter (not quite 11 yet at the time) wanted to do the same show and tell, with the same shirt and book ... and then snip off a corner of the shirt to turn into gun cotton to demonstrate how easy real munitions are to make. I nixed cutting up the shirt (too many memories), and recommended snipping a bit off of another T-shirt instead. Her school nixed that option[1], because children aren't supposed to know such things, and IT WOULD BE DANGEROUS!!! (the school's CAPS and punctuation). Model rocketry has been banned for the same reason, much to her deep dismay.
At just ten years old she was already on the "watch list" for her school district because she knows too much. What kind of useless milquetoasts are her generation going to become, anyway?
[0] That CD is still bound into the cover; I never bothered to take it out because it is available for the download online.
[1] Surprisingly, the hand-wringers & namby-pambys didn't try to have her arrested for bringing weapons to class.