My sister wants to divorce her husband because he's abusive. However, their only income comes from military disability that he receives. He's telling her that she can't get alimony from him because his government check is untouchable. Does anyone know if that's true?

Unfortunately that is correct. I guess she'll just either have to put up with him or get a job and support herself.

The thing is that divorce court may award her a claim, but there would be no way she can force any collection of the money

If the judge awards the wife alimony and he doesn't pay, she can ask the judge to hold him in contempt of court, and if he wilfully fails to pay, he risks going to the sheriff's motel, the local jail. The source of his funds doesn't matter.

The thing is that divorce court may award her a claim, but there would be no way she can force any collection of the money
This is so true. I know a few people that have done the same thing. Great answer