Why was the fugitive slave law of 1793 considered a danger to free blacks?

The Fugitive Slave Acts were a pair of federal laws that allowed for the capture and return of runaway slaves within the territory of the United States. Enacted by Congress in 1793, the first Fugitive Slave Act authorized local governments to seize and return escaped slaves to their owners and imposed penalties on anyone who aided in their flight. Widespread resistance to the 1793 law led to the passage of the Fugitive Slave Act of 1850, which added more provisions regarding runaways and levied even harsher punishments for interfering in their capture. The Fugitive Slave Acts were among the most controversial laws of the early 19th century.