in other words my ex would have to sign over his right to the dependents deduction.......Federal Law doesn't just trump state law as I was told by my tax man?
Federal Law always trumps state law, when the two are at issue, unless the federal government is infringing on the states general police power.
And even then, the state would have to take the federal government to court, which would be a constitutional law issue. (This is called federal supremacy)
You tax person is correct.
However, there has been a valid divorce decree violation, and unless the state court judge acquiesces (and they usually do) the judge could issue a contempt of court order against you.
If he did so, you can either suffer that order (pay the fine is probably as bad as it would get) OR take the state court decision to the federal district court.
You get the deduction
your answer got cut off