To not have a leg to stand on is to have no evidence or argument at all. He does not have a leg to stand on.
It is used most in disputes about rights and contracts. Anybody who does not have a leg to stand on is usually the last person to realise it.
1phrasenot have a leg to stand onTo have no evidence or argument at all.
“Without the receipt he did not have a leg to stand on.”
not have a leg to stand on is a phrase.
Practised in Idioms