As others have said, that is a legal question, not a tax question.
That said, what the judge has ordered is very common (that the non custodial parent claims the dependent every other year). Based on what we see in this forum, you're unlikely to get another judge to do it differently.
You (not him) have to sign form 8332 and give it to him to file with his tax return. If he tries to file the dependent on your year, there's simple fix. He can't "get away" with doing so.
Be aware, that there is a special rule in the case of divorced & separated (including never married) parents. When the non-custodial parent is claiming the child as a dependent/exemption/child tax credit; the custodial parent is still allowed to claim the same child for Earned Income Credit, Head of Household filing status, and day care credit. This "splitting of the child" is not available to parents who lived together at any time during the last 6 months of the year; then only one of you can claim the child for any tax reasons. The tax benefits may not be split in any other manner.
Note in particular that the non-custodial parent can never claim the Earned Income Credit, Head of Household filing status or the day care credit, based on that child, even when the custodial parent has released the dependency to him.
So, it's good idea to let the other parent know that you will be claiming those items, as many first time divorced parents are not aware of this rule and may try to claim those items, which will cause the IRS to send out letters.
