If there is no legal recourse for people brutalized by ICE, then it is de jure legal for them to do anything they want.
Remember what you said: "It also prevents people like Donald Trump from simply arresting his political opponents, based on nothing more than an accusation of guilt." It demonstrably doesn't prevent him from arresting, or killing, his political opponents.
He can, in fact, arrest his political opponents. He's doing it right now. There's no legal mechanism to stop him.