Sovereign immunity bars people from suing the government unless it agrees to be sued. The principle traces to English common law: 'the king can do no wrong.' The Eleventh Amendment embeds this protection for states, blocking most federal lawsuits against them without their consent. Federal sovereign immunity comes from judicial doctrine, not the Constitution's text. Congress chips away at this shield through statutes like the Federal Tort Claims Act, which lets people sue for injuries caused by government negligence—but with major exceptions. You can't sue for most intentional wrongdoing, discretionary decisions, or many law enforcement actions. States waive immunity selectively, often capping damages. The doctrine creates concrete absurdities: if a Postal Service truck hits you, you can sue. If an FBI agent falsely arrests you, you probably can't sue the government, only the individual agent. Sovereign immunity means government operates under fundamentally different legal rules than everyone else—a 13th-century monarchical principle that American courts inherited and have never fully reclaimed for a democratic system where accountability is supposed to be the whole point.