Retired Col. Ron Crews warns a ruling against the Defense of Marriage Act could put military chaplains at greater risk for discrimination.

Crews, who heads the Chaplain Alliance for Religious Liberty, said DOMA limited the impact when the 'don't ask, don't tell' policy was lifted and gays were allowed to serve openly in the armed forces.

Since DOMA is a federal law it governs the military. But Crews believes if it's overturned, chaplains who oppose homosexuality for religious reasons will be silenced and their careers damaged.

Gay rights advocates say DOMA dishonors gay veterans by denying benefits to their partners.