Where do you get that that covers permanent residents only? Your contract is what it is. I listed the justifications for termination of the contract. Until one of those events transpires, your contract is in force and your obligation remains.
So, that puts you between a rock and a hard place:
pay him his allowance or attempt to get him deported due to the illegal actions used to allow him to remain here.
Due to the complexities of the issue, I would surely run this past an immigration lawyer though before you do anything that might get you into legal trouble.

