Who can and cannot intercept taxes?

Do you mean tax refunds? Only government agencies.

Can my refund be used to pay other debts?

Under the law, state and Federal agencies refer to the IRS the names of taxpayers who are behind in their support payments, taxes, and loans. Your tax refund may not be refunded to you if you are delinquent in child or child and spousal support payments, have a past due Federal debt (such as a student loan), or owe state income taxes. Therefore, your refund will be used to pay other debts you owe. For additional information, refer to Tax Topic 203, Failure to Pay Child Support and Other Federal Obligations.

Additionally, someone who has won a court case from you in federal court can petition to have your federal refund garnished to settle that awarded amount from that court case.

This can be done for a state case as well, but it is MUCH more difficult because the plaintiff has to petition the federal court AFTER winning their case in state court.