VGLI (Veteran's Group Life Insurance) - ex-spouse as beneficiary?

If my divorce decree states that my ex-husband (retired military) has to keep me the beneficiary on his VGLI, can I legally enforce that ruling? I was told that the VGLI falls under Federal law, and according to Federal law, he can do whatever he wants with his VGLI, regardless of what the divorce decree says, since that is State law....