N.Y. Mental Hyg. Law § 9.15

§ 9.15 Informal admissions.\n The director of any hospital approved by the commissioner for such\npurpose may receive therein as an informal patient any suitable person\nin need of care and treatment requesting admission thereto. Such person\nmay be admitted as a patient without making formal or written\napplication therefor and any such patient shall be free to leave such\nhospital at any time after such admission.\n