The government of Australia has come under withering criticism for its harsh anywhere-but-here approach to refugees and other migrants who attempt to reach the country by boat. But instead of revisiting a cruel and costly policy — which involves sending everyone intercepted at sea to offshore prisons — Prime Minister Malcolm Turnbull has decided to double down.

His administration intends to propose legislation this week that would bar anyone who seeks to enter Australia without authorization and by boat from ever setting foot in the country. That would ban, among others, the approximately 1,200 people currently being held in camps in Nauru and Papua New Guinea from finding a legal way to even visit Australia, where some have relatives.

Mr. Turnbull billed the lifetime ban as a stern message to smugglers. “They must know that the door to Australia is closed to those who seek to come here by boat with a people smuggler,” he said last Sunday during a news conference. “It’s closed.” But his initiative targets refugees who are scrambling to find a haven amid the largest displacement crisis since World War II.

Australian lawmakers should oppose this proposal. Draconian immigration measures are often passed without due consideration for the human toll and opportunity cost they represent.