Judicial Review

Judicial review is the power of a court to review a law or an official act of a government employees or agent for constitutionality or for the violation of basic principles of justice. The court has the power to strike down that law, to overturn the executive act, or order a public official to act in a certain manner if it believes the law or act to be unconstitutional or to be contrary to law in a free and democratic society. http://en.wikipedia.org/wiki/Judicial_review

Judicial Branch constraint on the Executive Branch and Legislative Branch