If they're hungry, feed them. If they're thirsty, give them water. If they need shelter, give them shelter until the immigration department arrives. It's the human thing to do.
If the law says to turn them over to immigration, there's nothing inhumane about that, either. They'll still get food, water and shelter until they're deported.
The problem is, at least with the section of this proposed law I quoted above, that when the immigration department arrives, they may take the priest into custody as well. You really want that political PR mess on your hands?