Just out of curiosity...what would be the downside of writing a simple contract with your contractor (you're courting trouble if you don't draft one) stating that you will only pay for work performed by those legally permitted (I know that's a misnomer as they are de-facto permitted and de jure prohibited) to work in the country and that any suspicions to the contrary may constitute grounds for breach of contract.    I'm sure that the contractor would make a face or use a few swear words and you'd probably not get anything done. Disappointing that.