Answer:
In United States constitutional law, substantive due process is a principle allowing courts to protect certain fundamental rights from government interference, even if procedural protections are present or the rights are unenumerated (i.e not specifically mentioned) elsewhere in the US Constitution. Courts have identified the basis for such protection from the due process clauses of the Fifth and Fourteenth Amendments to the Constitution, which prohibit the federal and state governments, respectively, from depriving any person of "life, liberty, or property, without due process of law". Substantive due process demarcates the line between the acts that courts hold to be subject to government regulation or legislation and the acts that courts place beyond the reach of governmental interference. Whether the Fifth or Fourteenth Amendments were intended to serve that function continues to be a matter of scholarly as well as judicial discussion and dissent.[1]
Substantive due process is to be distinguished from procedural due process. The distinction arises from the words "of law" in the phrase "due process of law".[2] Procedural due process protects individuals from the coercive power of government by ensuring that adjudication processes, under valid laws, are fair and impartial. Such protections, for example, include sufficient and timely notice on why a party is required to appear before a court or other administrative body, the right to an impartial trier of fact and trier of law, and the right to give testimony and present relevant evidence at hearings.[2] In contrast, substantive due process protects individuals against majoritarian policy enactments that exceed the limits of governmental authority: courts may find that a majority's enactment is not law and cannot be enforced as such, regardless of whether the processes of enactment and enforcement were actually fair.[2]
The term was first used explicitly in 1930s legal casebooks as a categorical distinction of selected due process cases, and by 1952, it had been mentioned twice in Supreme Court opinions.[3] The term "substantive due process" itself is commonly used in two ways: to identify a particular line of case law and to signify a particular political attitude toward judicial review under the two due process clauses.[4]
Much substantive due process litigation involves legal challenges about unenumerated rights that seek particular outcomes instead of merely contesting procedures and their effects. In successful cases, the Supreme Court recognizes a constitutionally based liberty and considers laws that seek to limit that liberty to be unenforceable or limited in scope.[4] Critics of substantive due process decisions usually assert that there is no textual basis in the Constitution for such protection and that such liberties should be left under the purview of the more politically accountable branches of government.[4]