Dependent

It depends on your situation. Only the court order saying that you can claim your older child is not enough.

• If you are not the custodial parent, there is not much to do on your tax return. Per IRS regulations, only the parent who had custody for more than half the year can claim the children as dependents. The parent who had custody less than half the nights of the year can't claim them unless the parent with custody more than half the year, gives the other parent a signed dependent release Form 8332.
• If your older child stayed with you for more than half of the year, you can claim your child on your return. In this case, you will need to file by mailing your return because your older child has been claimed as a dependent on the other parent's return. 

You may bring this situation to the attention of the authority that issued the court order for the violation. 

This article may be of help to your situation.