What is the significance of the marbury vs. madison case?

Answer:
judicial review

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It allowed the federal government to run roughshod over the states. John Marshall -- geez, what a Chief Justice. What a shame.

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In short, it established the principle of judicial review by the courts to decide the constitutionality of laws or statutes passed by the legislative and/or executive branches.

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It set important prescient, one that is still used today.