Reid follows three Maryland cases, decided between 1812 and 1820, to show a state moving within two decades from enlarging black freedom to writing proslavery doctrine into its courts.

Petitioners of Haitian origin pressed an argument few others could make: that the French decree of 1794 had freed them, and that Maryland owed comity to the law of the territory they came from. Early on the bench was receptive, treating illegal importation as grounds for freedom in the spirit of Somerset. As alarm over the rebellion in Haiti spread and the Missouri Compromise hardened the categories of slave and free soil, the reception changed; by the last of the three cases the slaveholder's claim prevailed outright.

Those decisions, Reid argues, laid groundwork for the refusal of comity between states that Dred Scott would complete, and they expose a state that could not decide whether it was slave or free.