It seems like the question is missing some context related to a specific historical event or document regarding slavery. However, based on common historical knowledge, particularly related to the U.S. Constitution and the compromise around slavery made during the founding of the United States, the appropriate answer would likely be:
They decided that the slave trade could not be banned until 1808.
This choice refers to the Constitutional compromise allowing the slave trade to continue until that year. If you have more details or a different context, feel free to provide them!