.Mom brings kid to visit dad in another state, dad tells her she can't take child back with her to home state
It sounds like you need to talk to a lawyer as soon as possible. You may want to start out talking to a lawyer in your home state to see if you can file there for an emergency custody order and/or talk to a lawyer in the state where the child currently is to see about the possibility of filing anything in court there. Some factors that may be important to discuss with the lawyer are if there is a current custody order; whether the father’s paternity has been legally established; and to figure out which state is the child’s “home state” (generally where the child has lived for the past 6 months consecutively but there are exceptions).
If you are considering trying to take the child back to the home state (where you live with the child) without going through the courts, I STRONGLY suggest calling a local lawyer who specializes in custody in [OTHER STATE] to check that you may not be possibly violating any [OTHER STATE] law by returning to your home state with the child against the other parent’s wishes. You may even want to check with a local police precinct in [OTHER STATE] if you can’t contact a lawyer. Here is a link to lawyers, free and paid for both states: LINK