In the common law, and under many statutes, standing or locus standi is the ability of a party to demonstrate to the court sufficient connection to and harm from the law or action challenged to support that party's participation in the case. In the United States, for example, a person cannot bring a suit challenging the constitutionality of a law unless the plaintiff can demonstrate that the plaintiff is (or will be) harmed by the law. Otherwise, the court will rule that the plaintiff "lacks standing" to bring the suit, and will dismiss the case without considering the merits of the claim of unconstitutionality. In order to sue to have a court declare a law unconstitutional, there must be a valid reason for whoever is suing to be there. The party suing must have something to lose in order to sue unless they have automatic standing by action of law.
There are a number of requirements that a plaintiff must establish in order to have standing before a federal court. Some are based on the case or controversy requirement of the judicial power of Article Three of the United States Constitution, § 2, cl.1. As stated there, "The Judicial Power shall extend to all Cases . . .[and] to Controversies . . ." The requirement that a plaintiff have standing to sue is a limit on the role of the judiciary and the law of Article III standing is built on the idea of separation of powers. Federal courts may exercise power only "in the last resort, and as a necessity".
Additionally, there are three major prudential (judicially-created) standing principles. Congress can override these principles via statute, but Congress cannot change the three constitutional standing requirements.
In the suit, parents of black public school children alleged that the Internal Revenue Service was not enforcing standards and procedures that would deny tax-exempt status to racially discriminatory private schools. The Court found that the plaintiffs did not have the standing necessary to bring suit. Although the Court established a significant injury for one of the claims, it found the causation of the injury (the nexus between the defendant’s actions and the plaintiff’s injuries) to be too attenuated. "The injury alleged was not fairly traceable to the Government conduct respondents challenge as unlawful".
In another major standing case, Lujan v. Defenders of Wildlife, the Supreme Court elaborated on the redressability requirement for standing. The case involved a challenge to a rule promulgated by the Secretary of the Interior interpreting §7 of the Endangered Species Act of 1973 (ESA). The rule rendered §7 of the ESA applicable only to actions within the United States or on the high seas. The Court found that the plaintiffs did not have the standing necessary to bring suit, because no injury had been established. The injury claimed by the plaintiffs was that damage would be caused to certain species of animals and that this in turn injures the plaintiffs by the reduced likelihood that the plaintiffs would see the species in the future. The court insisted though that the plaintiffs had to show how damage to the species would produce imminent injury to the plaintiffs. The Court found that the plaintiffs did not sustain this burden of proof. "The 'injury in fact' test requires more than an injury to a cognizable interest. It requires that the party seeking review be himself among the injured".
Beyond failing to show injury, the Court found that the plaintiffs failed to demonstrate the standing requirement of redressability. The Court pointed out that the respondents chose to challenge a more generalized level of Government action, "the invalidation of which would affect all overseas projects". This programmatic approach has "obvious difficulties insofar as proof of causation or redressability is concerned".
However, the Supreme Court has also held that taxpayer standing is constitutionally sufficient to sue a municipal government in a federal court. States are also protected against lawsuits by their sovereign immunity. Even where states waive their sovereign immunity, they may nonetheless have their own rules limiting standing against simple taxpayer standing against the state. Furthermore, states have the power to determine what will constitute standing for a litigant to be heard in a state court, and may deny access to the courts premised on taxpayer standing alone.
In the U.S. Commonwealth of Virginia, the Supreme Court of Virginia has more-or-less adopted a similar rule. An individual taxpayer generally has standing to challenge an act of a city or county where they live, but does not have general standing to challenge state expenditures.
Frequently a litigant wishes to bring a civil action for a declaratory judgment against a public body or official. This is considered an aspect of administrative law, sometimes with a constitutional dimension, as when the litigant seeks to have legislation declared unconstitutional.

Public-interest standing is also available in non-constitutional cases, as the Court found in Finlay v. Canada (Minister of Finance).
In British administrative law, the applicant needs to have a sufficient interest in the matter to which the application relates. This sufficient interest requirement has been construed liberally by the courts. As Lord Diplock put it:
"[i]t would...be a grave lacuna in our system of public law if a pressure group...or even a single public spritied taxpayer, were prevented by outdated technical rules of locus standi from bringing the matter to the attention of the court to vindicate the rule of law and get the unlawful conduct stopped.