Judicial oversight

Judicial review is a process under which executive and (in some countries) legislative actions are subject to review by the judiciary. A court with judicial review power may invalidate laws and decisions that are incompatible with a higher authority; an executive decision may be invalidated for being unlawful or a statute may be invalidated for violating the terms of a written constitution. Judicial review is one of the checks and balances in the separation of powers: the power of the judiciary to supervise the legislative and executive branches when the latter exceed their authority. The doctrine varies between jurisdictions, so the procedure and scope of judicial review may differ between and within countries.

Judicial review can be understood in the context of two distinct—but parallel—legal systems, civil law and common law, and also by two distinct theories of democracy regarding the manner in which government should be organized with respect to the principles and doctrines of legislative supremacy and the separation of powers.

First, two distinct legal systems, civil law and common law, have different views about judicial review. Common-law judges are seen as sources of law, capable of creating new legal principles, and also capable of rejecting legal principles that are no longer valid. In the civil-law tradition, judges are seen as those who apply the law, with no power to create (or destroy) legal principles.

Secondly, the idea of separation of powers is another theory about how a democratic society's government should be organized. In contrast to legislative supremacy, the idea of separation of powers was first introduced by Montesquieu; it was later institutionalized in the United States by the Supreme Court ruling in Marbury v. Madison under the court of John Marshall. Separation of powers is based on the idea that no branch of government should be able to exert power over any other branch without due process of law; each branch of government should have a check on the powers of the other branches of government, thus creating a regulative balance among all branches of government. The key to this idea is checks and balances. In the United States, judicial review is considered a key check on the powers of the other two branches of government by the judiciary.

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