Yes! While marijuana usage is rarely prosecuted to the full extent of the law New York, it is still illegal within the state.
Smoking marijuana in private is only punishable by a $100 fine, but additional arrests carry harsher penalties. Smoking in public, however, is a B misdemeanor and can be punished by up to six months in jail.
Most first time offenders are offered a Marijuana Adjournment in Contemplation of Dismissal (MACD), which essentially dismisses the charges if are not arrested again within one year.
BUT I HAVE A LICENSE TO SMOKE MARIJUANA IN ANOTHER STATE?
Sorry but no, marijuana is still illegal in New York. Licenses or prescriptions from other states are not valid in New York.