My question involves criminal law for the state of: Texas

My son was arrested in 2002 for family violence at the age of 16. He received deferred adjudication and six months probation with community service and it was dismissed. My son has served four years in the military and is now in the police academy; he has interviewed with several police agencies in our state and one of them sent him a letter of refusal stating that they could not hire him because of the charge he received in 2002 at the age of 16. He did not realize this would be an issue since he was a minor; is this a law in the state of Texas? Is there any recourse?

Thank you