Why is selective incorporation important? It reserves all powers not delegated to the federal government to the state governments.

It established affirmative action.

It established federalism.

It extends the civil liberties provided in the US Bill of Rights to state governments.

So big picture, selective incorporation, it's the doctrine where judicial decisions incorporate rights from the Bill of Rights to limit laws from states that are perceived to infringe on those rights, and the justification comes from the 14th Amendment.  It refers to the legal doctrine the U. S. Supreme Court has employed over the years to extend the rights guaranteed by the U. S. Constitution to the states. Through selective incorporation, the Court has ruled that states may not pass laws restricting many of the important rights enshrined in the Constitution.

Selective incorporation is a doctrine written into the Constitution that protects American citizens from their states' enacting of laws that could infringe upon their rights. Selective incorporation is not a law, but a doctrine that has been established and confirmed time and again by the United States Supreme Court.

The idea of selective incorporation dates to when the Constitution was being drafted, with the founding fathers heatedly debating the power of state governments versus the power of the federal government. In the end, the Constitution was signed and enacted without any definitive conclusion on the issue. In the 1833 case of Barron v. Baltimore, the Supreme Court ruled that the Bill of Rights applied only to the federal government, meaning that states were able to pass their own laws violating the Bill of Rights without any intervention by the federal government.  It wasn't until 1868 that Congress passed the 14th Amendment, forbidding states from denying anyone the freedom to life, liberty, and property without due process, thus reversing the decision of Barron v. Baltimore.  Beginning in the 1920s, the Supreme Court ruled on many cases about the protection of the Bill of Rights within state laws. Selective incorporation is based on this approach to choosing which clauses of the Bill of Rights apply to state governments.  As the Supreme Court continued to rule on cases challenging state governments' ability to violate the Bill of Rights, justices began to debate the application of the 14th Amendment. Some felt that the amendment applied to the all amendments in the Bill of Rights, prohibiting states from the same violations as the federal government, while others felt that only portions of those basic rights should be incorporated. In the 1937 case of Palko v. Connecticut, the Court rejected total incorporation and adopted the doctrine of selective incorporation as well as the guidelines for applying it.

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that is probably something for you to answer