In August 1836, Chief Justice Lemuel Shaw ruled that slaves brought to Massachusetts "for any temporary purpose of business or pleasure" were entitled to freedom.

Curtis argued that the doctrine of comity required Massachusetts to respect the laws of Louisiana, and therefore Mrs. Slater should be allowed to bring Med home with her.

[6] When giving his opinion, Shaw discussed several precedents in international law, including the British case of Somerset v. Stewart (1772), and the abolishment of slavery in Massachusetts.

Connecticut used it in Jackson v. Bulloch (1837); New York and Pennsylvania used it in legislation declaring that slaves became free when brought to those states; and Ohio courts began using it in 1841.

By the start of the Civil War, every Northern state other than Indiana, Illinois, and New Jersey granted freedom automatically to any slave brought within its borders.