If you create one to prank your friend, and he ends up falling for it and sharing it in another group, and it gets to someone who alerts the authorities, without including the context of "this was sent to me by a guy who's a bit of a joker", and railway management's policy is to take all reports seriously rather than verifying their provenance...I find it hard to think anyone in that chain should really be held liable.

Intent is a valid legal concept. Certainly there's no way to try "swatting" without crossing that line of intent, but (for example) less-threatening prank phone calls can be in the grey area.

I presume there is established legal practice for handling these kinds of things, but for generative images the legal limits won't achieve wide awareness until some teenagers and assorted morons get hauled into court.

intent is very difficult to prove.

"I was just memeing, sir"