Definition
The incorporation doctrine is the constitutional principle that most protections in the Bill of Rights, which originally limited only the federal government, also bind state and local governments. The doctrine works through the Fourteenth Amendment.
Before incorporation, a state could in theory abridge speech or skip certain criminal-procedure protections without violating the federal Constitution. Incorporation closed that gap for most rights.
Why it matters
How it works
Courts located the Bill of Rights guarantees within the Fourteenth Amendment promise that no state shall deprive a person of liberty without due process of law. A right deemed fundamental to ordered liberty is treated as part of that protected liberty.
Incorporation has proceeded right by right over many decades rather than all at once, an approach known as selective incorporation. Most provisions are now applied to the states, with only a few minor exceptions remaining.