You cannot flirt in public.

The Law Explained

To crack down on unsolicited advances and street harassers bothering women on the street, early 20th-century New York passed a law making flirting punishable by a $25 fine. Men who stared too intensely, made inappropriate comments, or otherwise annoyed women in public spaces could be swiftly hauled off by the police. While well-intentioned for its time, prosecuting a wink in modern Manhattan would completely overflow the courts.