npub19fywau9ff6pjmjek7k4kukgdcdf7w4chne57upj5s7y87gk7v27qx7n5nv (npub19fy…n5nv)
The changes required by the Fugitive Slave Act made slavery a northern problem, bringing a lot of visibility to the issue, and probably was a major factor in the popular opinion of the north turning from tolerance to opposition.
It wasn't enforcing existing laws - it was a complete corruption of them.