UK Home Secretary Theresa May has a new proposal that would force international students at British universities to leave the country immediately after graduating, making it far more difficult for them to get work visas and remain in the UK. I was reluctant to write about this because I myself could be personally affected–I’m starting a PhD at Cambridge this autumn, and I am certainly interested in the possibility that I might get a job in the UK when I finish. I generally try to avoid topics where I have a significant personal stake that might bias my analysis. But in this case, the arguments against the policy are too clear and too definitive. Even if you ignore the interests of foreign students like me, this is an irrational policy that does unequivocal, quantifiable harm to Britain.