Established the power of judicial review.

Affirmed the federal government's implied powers.

Established 'clear and present danger' test- an important principle in First Amendment jurisprudence.

Overturned 'separate but equal' doctrine. State-sponsored racial segregation in public schools declared unconstitutional. 

Prohibited state-sponsored prayer in public schools.

Outlined that legislative apportionment is a justiciable non-political question. 

Established the right to counsel for criminal defendants.

Established important protections for student free speech rights in public schools.

A major victory for freedom of the press.

Interpreted the Free Exercise Clause by constructing a three-part test intended to balance state educational interests against the interests of religious freedom. 

Decided that redistricting can be held to the same legal standard as laws that explicitly classify by race. 

Preserved the system of federalism; had significant implications for the interpretation of the Commerce Clause. 

Had significant implications for the Second Amendment and gun rights in the United States.

Had a significant impact on campaign finance laws in the United States.