be (someone's) funeral
A (usually humorous) threat indicating that if someone does or doesn't do something, it will bring about negative consequences. OK, fine, don't do what mom said. It's your funeral! If Billy goes in my room when I'm not here, it'll be his funeral.
it's (or that's) someone's funeral
used to warn someone that an unwise act or decision is their own responsibility. informal 1996 Amitav Ghosh The Calcutta Chromosome I'll turn a few pages for you; but remember, it was you who asked. It's your funeral.