Sovereign immunity

From The Legal Information Institute:

The sovereign immunity refers to the fact that the government cannot be sued without its consent. 

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Sovereign immunity was derived from British common law doctrine based on the idea that the King could do no wrong. In the United States, sovereign immunity typically applies to the federal government and state government, but not to municipalities. Federal and state governments, however, have the ability to waive their sovereign immunity. The federal government did this when it passed the Federal Tort Claims Act, which waived federal immunity for numerous types of torts claims. 

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When determining whether a citizen may sue a state actor (someone acting on behalf of the state: i.e. a state worker), courts will typically use one (1) of four (4) tests:

  1. Governmental v proprietary function test (Was the actor functioning in a governmental fashion or a proprietary fashion?)
    1. If the actor was performing a proprietary function (i.e. acting for financial gain for itself or its citizens; doing something that is not historically a governmental function; doing something that can be performed by a private corporation/contractor), then the actor is subject to liability
    2. If the actor was performing a governmental function (i.e. acting for the general public; doing something ordained by legislature; performing a historic gov function), then the actor is not subject to liability
  2. Ministerial/operational v. discretionary functions/acts test (Was the actor performing a ministerial/operational task or a discretionary task?) 
    1. If the actor is performing a ministerial/operational action, then there is not immunity. 
    2. If the actor is performing a discretionary action, then there is immunity.
  3. Planning v implementational (Was the actor planning an action or implementing an action?)
    1. If the actor’s planning of policy results in harm, then there is immunity
    2. If the harm happens due to the government’s implementation of the plan, then there is not immunity  
  4. Non-justiciable v. justiciable
    1. If the action is justiciable under regular tort principles, then there is no immunity. If the issue is not justiciable under regular tort principles, then there is immunity.

Link to the rest at The Legal Information Institute

And, since you were curious about what justiciabile means:

Justiciability refers to the types of matters that a court can adjudicate.  If a case is “nonjusticiable,” then the court cannot hear it. Typically to be justiciable, the court must not be offering an advisory opinion, the plaintiff must have standing, and the issues must be ripe but neither moot nor violative of the political question doctrine. Typically, these issues are all up to the discreion of the court which is adjudicating the issue. 

More about justiciability at The Legal Information Institute