What's the difference between regulating and restricting the supply of authorized (human) workers, and robots? Why is it OK to hire non-citizen robots but it's

What's the difference between regulating and restricting the supply of authorized (human) workers, and robots? Why is it OK to hire non-citizen robots but it's not OK to hire non-citizen humans? Whichever political party has the ear of working people disenfranchised in meaningful numbers from their jobs, will absolutely consider regulating robots every bit as much as they regulate immigrant workers. Protectionism is a trap every party has fallen into from time to time.