Are you sure the mayor has delegable arrest authority?
And even if he did, arrest authority is still subject to certain rules. If the police have not witnessed a crime, or have reasonable suspicion of a crime, or some other immediate public safety concern, they cannot lawfully arrest someone without a warrant.
Nobody in New York City has the authority to arrest someone just because they want to. Not the mayor. Not the commissioner of police. Not the cops themselves. Not even judges.
The whole concept is blatantly anti-social and unjust. You shouldn't let your fetish for "international law" blind you to Mamdani's stupidity.
What authority has jurisdiction over Netanyahu, that they can lawfully order his arrest for ignoring their mandates?
Not might. Absolutely would be illegal.
Mamdani's fantasy that the office of the mayor of New York city is an enforcement arm of the IPCC is as perverse as it is insane. Very on brand for the people whose votes won him the Democrat primary.