A 17 year old male child has sexual intercourse with a significantly (at least two decades) older man.
In New York, where the child's residence is, this is, I think, legal. At the time of the incident, however, the child was staying in California, where this is, I think (same source), illegal, for a period of two months.
The state of residence of the adult is unknown.
Which state's laws apply? Can the adult be prosecuted?