What was important about the Trade Compromise where slavery was involved? The Congress was allowed to place a tariff on the slave trade in the South. It gave abolitionists hope that the slave trade could be brought back to life again. The Congress was not allowed to place any tariff on the slave trade for twenty years. Although it seemed that the South had won, it gave abolitionists hope that the slave trade could be brought to an end by means of tariffs in a fairly short period of time. The Congress was not allowed to place any tariff on the slave trade for fifty years. It gave slave owners more possibilities in trading of their slaves.