The primary requirement for receiving a U.S. passport—a valuable form of identification, as well as a crucial document for foreign travel—is being a citizen of the United States.
(For more information on how to go from having a green card to receiving U.S. citizenship, see How to Become a U.S. Citizen.) And for information on how to get or renew a passport, see the State Department's How Do I Apply for a Passport? page.
Even being a U.S. citizen is not, however, enough in some cases. Under a program called "Passport Denial," authorized by a 1997 amendment to a law called the Personal Responsibility and Work Opportunity Reconciliation Act (PRWORA), any person who owes child support in an amount greater than $2,500 will be denied a U.S. passport until the matter is cleared up. (See the Social Security Act at 42 U.S.C. Section 652(k).) This doesn't affect your U.S. citizenship, but it will affect your right to return to the United States after foreign travel.
At one time, the threshold was $5,000, but it was lowered to $2,500 in 2007.
If the person already has a passport, the U.S. government can revoke, restrict, or limit its use. (As a practical matter, however, they are normally unable to do that without having physical access to the passport, such as during a request for renewal.)
The U.S. Passport Agency automatically receives information from a database list kept by the U.S. Department of Health and Human Services (HHS). The information in this database originally comes from county district attorney offices that work on child support enforcement, which reports support amounts owed ("arrearages") to HHS through state or local child support agencies.
The people at U.S. passport services offices have no information concerning your child support obligations and no authority to do anything until HHS removes your name from its list. Don't call HHS, though—you first need to contact your state, local, or tribal child support agency to make arrangements to pay your child support debt or otherwise reach some satisfactory agreement.
If you owe child support in more than one U.S. state, then it is likely that all of them reported your name to the Passport Denial program. In that case, you will need to negotiate with all of them before you can be cleared to receive a U.S. passport. To find the relevant agency, see the Find a Local Child Support Office page of the HHS website.
Once you have paid off the child support debt or come to some satisfactory agreement, the office(s) you've dealt with will request that HHS remove your name from the database list. This typically takes two or three weeks.
Assuming you have already submitted an application to the U.S. Passport Agency, and received notification of the intended denial, this office will hang on to your application for up to 90 days. If you can manage to clear up the child support problem within that time, the Passport Agency will process your application and mail the passport to you.
If you are having trouble getting action on your application, contact the office of the National Passport Information Center (NPIC).