Abreviated as F.U.C.K.
Back in the Middle Ages, this was a reason to be put to shame. For Unlawful Carnal Knowledge, also known as fuck, was a form of rape and illegal act in the Middle Ages.
A euphemistic way of referring to taboo sex (outside of marriage, adultery, homosexuality, sodomy, etc.), this phrase is often used as a false etymology for the word "fuck"
Also, Van Halen's 1991 album
I remember coming home and getting slapped by my dad for unlawful carnal knowledge, apparently he found out my "roomate" and I were actually dating
Person 1: I am not unlawful. I did not commit war crimes in France.
Person 2: I, too am not unlawful and instead a normal citizen, i did not commit war crimes in France like you, nor anything such as: murder, tax evasion, theft, or anything that abides the law.