The law is nullified and may not be enforced against anyone, but it is not "repealed" in the sense that a legislature repeals laws it has made earlier. The unconstitutional law will remain on the books until the appropriate legislature makes an actual repeal to clear the books of the now useless law.
If a law is challenged in court or is relevant to a case appealed to the US Supreme Court, and the US Supreme Court declares the law unconstitutional, it will be nullified, or overturned. Unconstitutional laws are unenforceable.
The Supreme Court of the Unites States may declare laws unconstitutional. It is the only branch legally able to do that.
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who decides whether or not the supreme court will review a case
who decides whether or not the supreme court will review a case
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