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In 1837 Edward Prigg caused a fugitive Maryland slave-woman to be returned to her mistress, in violation of a Pennsylvania statute forbidding the carrying of any negro out of the State in order to enslave him. The case was finally brought before the Supreme Court of the United States, where it was contended that the statute was unconstitutional since it conflicted with the National Fugitive Slave Act of 1793. The opinion was handed down that the national law must be carried out by national authorities alone.