There would have been no need for a fugitive slave law, either in 1793 or 1850, had slaves not escaped regularly, and in such numbers, that their activities came to be seen as a threat to the survival of the slave system. Taking as its point of departure the passage of the 1850 Fugitive Slave Law, this study focuses on the many ways the enslaved, by fleeing their enslavement, raised questions both about the law's legitimacy and the economic and political system it was meant to protect. As a Cleveland editor put it on the eve of the Civil War, in struggling for their freedom, slaves, by their actions, were responsible for starting “an ‘underground railroad’ system of escape” that, over the years, had amassed an impressive record of success, even if it had not totally undermined the system of slavery. Their actions were sustained by informal networks and alliances in slaveholding communities, by abolitionists who opposed the law, by those who had no particular aversion to the law but who were dragged nonetheless into the political maelstrom caused by efforts to reclaim fugitives from slavery in free states, and by the concerted efforts of black communities, large and small, urban and rural, that openly defied the implementation of the law. If it is true that laws can only gain their legitimacy by being assented to by all they wish to bind, then the 1850 Fugitive Slave Law was doomed to failure from its very inception. It met with strong opposition in and out of Congress for its violations of bedrock principles of jurisprudence and for its pandering to slave interests, which had been clamoring, for some time, for a more effective law to facilitate the recapture of escaped slaves, or, as the Constitution denominated them, “fugitives from labor.” Slaveholding interests unabashedly declared that on its passage and enforcement rested the future of the Union. Many observers were convinced, however, that nowhere in the Constitution was Congress expressly granted the power to enact such a law. Yet advocates thought it did and their position carried the day. The result was a law that nationalized the recapture of fugitive slaves. Consequently, every effort to retake an escapee had the potential to create deep political crises in the communities in which it occurred.