In his Summary View of the Rights of British America (1774), Thomas Jefferson asserted, somewhat disingenuously, that Virginians favored the "abolition of domestic slavery" and that as the first step toward this end, "it is necessary to exclude all further importations from Africa." He complained, however, that "our repeated attempts to effect this by imposing duties which might amount to a prohibition, have been hitherto defeated by his majesty's negative." In his first draft of the Declaration of Independence, Jefferson condemned the Crown in more forceful language, asserting that the king had "waged cruel war against human nature itself, violating its most sacred rights of life and liberty" by perpetuating the African slave trade. Calling it "piratical warfare," Jefferson asserted that "a CHRISTIAN king of Great Britain" was so "Determined to keep open a market where MEN" were bought and sold that he used his "negative" to suppress "every legislative attempt to prohibit or to restrain this execrable commerce."
The Continental Congress removed Jefferson's tirade from the Declaration, in part because it simply did not ring true. The colonists, for the most part, had been willing and eager purchasers of slaves. Nor is there any evidence that either Jefferson or any of the other leaders of Virginia had any interest in actually ending slavery. Virginia's attempt to ban the trade was purely economic, and not based on any moral opposition to slavery. Similarly, the Crown's refusal to allow them to limit or end the trade was economic.
During the Revolution, all of the new states banned or suspended the international slave trade. Most slaves arrived on English ships, and even those on American ships were purchased from agents of the Royal African Company stationed on the west coast of Africa. Thus, all the colonies (which soon became the states) banned the African slave trade as part of their overall policy of refusing to import anything from Britain. The "non-important" movement was an attempt to cut all economic ties with Britain. Since most slaves were brought in by British ships, and virtually all were purchased from the British on the coast of Africa, a ban on the trade was an important part of the colonists' general policy not to trade with Britain.
In some of the northern colonies, abolition of the slave trade had a moral as well as an economic basis. Opposition to slavery was growing, and during or immediately after the Revolution, five states would either end it outright (Massachusetts and New Hampshire) or pass gradual abolition acts (Pennsylvania, Rhode Island, and Connecticut) that would lead to a relatively speedy end to slavery. In those states, a ban on the international slave trade was consistent with growing opposition to slavery itself. In the remaining new states, where slavery was central to the economy, opposition to the trade was economic and political, but not essentially moral. After the Revolution, South Carolina reopened its international trade, but then suspended it in 1785 because of the ongoing depression in the state. Similarly, North Carolina levied a prohibitive tax on newly imported slaves and then in 1794 banned the trade altogether. The trade remained open in Georgia in 1787, but in the wake of the Haitian Revolution, that state also banned it.
The Revolution brought freedom to slaves who joined the armies or escaped in the chaos of war. Thousands left South Carolina and Georgia when the British Army evacuated those states. Some of these people remained free, while others ended up being re-enslaved in the British Caribbean. At the end of the war, leaders in the Deep South fully expected to reopen the trade at some point, to replenish their slave holdings. However, in 1787, when the Constitutional Convention met in Philadelphia, no American state except Georgia had yet reopened the African trade. Nevertheless, with the expectation of reopening the international slave trade, the delegates from the Deep South jealously guarded their right to import more slaves. They succeeded with the provision in Article 1, Section 9 of the Constitution, which prevented Congress from ending the trade before 1808.