who am I, are you, etc. to do something?

Who is (one) to (do something)?

What right or authority does one have to do something. I pay my rent and my share of the bills—who is he to judge how I spend my money otherwise? It didn't make sense to me, but then who am I to question the court's decision?
See also: who

who am ˈI, are ˈyou, etc. to do something?

used when you think somebody has no right or authority to do something: Who are you to tell me I can’t leave my bicycle here? It’s not your house.I don’t agree, but then who am I to say what she should do?
See also: who