a hanging offence
A crime, misdeed, or impropriety that is (hyperbolically) perceived to warrant death by hanging. Primarily heard in US. Political correctness has become so authoritarian these days that saying anything with even the slightest derogatory implication is seen as a hanging offense!
a hanging offencea fault or crime so serious that the perpetrator should be executed.
1998 Spectator It is hardly a hanging offence to overlook telegrams about a small African country, but surely the Prime Minister must read JIC reports?