<Ul> <Li> Signed into law by President Thomas Jefferson on March 2, 1807 </Li> </Ul> <Li> Signed into law by President Thomas Jefferson on March 2, 1807 </Li> <P> The Act Prohibiting Importation of Slaves of 1807 (2 Stat. 426, enacted March 2, 1807) is a United States federal law that stated that no new slaves were permitted to be imported into the United States . It took effect in 1808, the earliest date permitted by the United States Constitution . </P> <P> This legislation was promoted by President Thomas Jefferson, who called for its enactment in his 1806 State of the Union Address . He had promoted the idea since the 1770s . It reflected the force of the general trend toward abolishing the international slave trade, which Virginia followed by all the other states had prohibited or restricted since then . South Carolina, however, had reopened its trade . Congress first regulated against in the Slave Trade Act of 1794 . The 1807 Act ended the legality of trade with the U.S. However, it was not always well enforced and slaves continued to be smuggled in limited numbers . All the northern states had ended slavery by 1804, but ownership remained legal in all the Southern states . The 1807 law did not change that--it just made importation from abroad a crime . The domestic slave trade within the U.S. was unaffected by the 1807 law . Britain, the major power involved in the Atlantic slave trade, passed the comparable Abolition of the Slave Trade Act that same month . </P>

What restriction did the united states congress place on slavery in 1808