The Adams-Onis Treaty which was made in 1819 was originally based on Spain handing over Florida territory to the United States.
However, it also established the United States to forfeit the territory of Spanish Texas and its surrounding areas around the west of the Sabine River.
Hence, in this case, it is concluded that the Adams-Onis Treaty "Set the eastern and northern borders of Texas."
Answer: Slaves could not bring a civil suit to the supreme court because the Supreme Court says that blacks cannot be citizens and that Congress has no power to outlaw slavery in any territory.