was anything done to stop it?
Congress would have the power to ban the international slave trade, but not for another twenty years. In exchange for this concession, the federal government's power to regulate foreign commerce would be strengthened by provisions that allowed for taxation of slave trades in the international market.
Constitutional Convention (United States)
 Congress would have the power to ban the international slave trade, but not for another twenty years (that is, not until 1808). In exchange for this concession, the federal government's power to regulate foreign commerce would be strengthened by provisions that allowed for taxation of slave trades in the international market and that reduced the requirement for passage of navigation acts from two-thirds majorities of both houses of Congress to simple majorities.
what took place at the constitutional convention of 1787 The result of the convention was the creation of the Constitution of the United States. was slavery an important topic in it? Yes.
wiki:6129163
Constitutional Convention (United States) [SEP] Commerce and Slave Trade Compromise
During the convention's late July recess, the Committee of Detail had inserted language that would prohibit the federal government from attempting to ban international slave trading and from imposing taxes on the purchase or sale of slaves. The convention could not agree on these provisions when the subject came up again in late August, so they referred the matter to an eleven-member committee for further discussion. This committee helped work out a compromise: Congress would have the power to ban the international slave trade, but not for another twenty years (that is, not until 1808). In exchange for this concession, the federal government's power to regulate foreign commerce would be strengthened by provisions that allowed for taxation of slave trades in the international market and that reduced the requirement for passage of navigation acts from two-thirds majorities of both houses of Congress to simple majorities.