Absolutely not!! If the substantial change in circumstances exists, she may have the ability to go back to court to claim spousal maintenance. However, the article suggests that he may be having trouble making the rent with the current arrangement and, if he can't provide for the child's shelter properly, he will lose custody of the child. If this is simply about dollars and cents on the part of the ex, her option is spousal maintenance. If not, he should be entitled to get the money back since the time the child moved in with him and the child support due to him from her. The attitude of allowing this sort of thing to continue is what allows it to continue.