If nothing has been filed, there is nothing, generally, that prevents a parent from relocating. THe remedy is to file a divorce, legal separation or custody action and seek an order,by ex parte relief in some cases, for the child's return.
---------->> Yes, BUT... he states she is his EX wife, which would indicate that something HAS been filed, namely a divorce. He also mentions elsewhere that she did not FILE for a relocation, which, POST-divorce WOULD be the appropriate action.
NOW, per NY, there ISN'T a law regarding relocation AND unless you actually HAVE a restriction IN your divorce papers? You're FREE to go wherever you like, AS LONG AS, you maintain the existing visitation. Sooo, there MAY not be ANYTHING "illegal" about what his ex wife has done, per NYS, as long as, she maintains their existing visitation schedule.
Now, if he has mis-stated what his marital status is? THAT changes things; however, if they are indeed divorced and/or separated under a Stipulation of Settlement, and there is not a SPECIFIC move away restriction (which the standard here is 25 miles, although some lawyers use 50), what I said holds true.
If she is failing to meet their visitation schedule, he can file contempt charges against her, and have her served in FL, she will have to return to NY to respond.
But again, all of this is purely conjecture since the OP hasn't provided enough information on which to go on.