I say, let him stay in Spain.
If he's returned, there's going to be the cost of prosecuting him, then the cost of imprisoning him for the 3-5 years he'll likely have to serve time (if that much). And then he's going to be deported again, anyway.
Leave him where he is.
At least he'll be out of here, never to return.
If he ever tries to come back, re-deport him to Uganda, or that other little country that has agreed to take some...