By what law does the Supreme Court decide if a law is constitutional?

Answer 1

Yes, the Supreme Court can determine that a federal or state law is unconstitutional.

Answer 2

The Supreme Court decides if a law is constitutional based on the principle of judicial review, which is not explicitly mentioned in the Constitution but was established by the Court itself in the landmark case Marbury v. Madison (1803). This principle gives the Court the power to interpret the Constitution and determine if a law aligns with its provisions. The Court uses this authority to assess whether a law violates any constitutional rights or principles.