Washington, D. C. - Thomas Jefferson signed the Act Prohibiting Importation of Slaves. It went into effect, January 1st, 1808.
This did not abolish slavery. It did not emancipate the enslaved. It only made the entry of enslaved people, into the United States, illegal.
London, England - The Parliament of the United Kingdom passed An Act for the Abolition of the Slave Trade. This Act ended the Transatlantic Slave Trade, by law, in the United Kingdom.
Great Britain stopped slavery, in 1772, in the country. It was due to a ruling from Somerset's Case, of that year. It was ruled that slavery had no place on English soil. This had no effect on slavery in the British colonies. The law that barred it in the colonies came later, in 1833.
After the United States formed, the African slave trade became less profitable for Britain. Its slave sugar colonies in the Caribbean needed lots of support. Sugar competition, from Spanish Cuba and Portuguese Brazil hurt. Add to that, Britain needed its navy for its India colonies.
British-made sugar was a costly effort. Instead, Britain found that trade, with Portugal and Spain, for their sugar was better. British finished goods were sent to pay for the sugar. This led to more profit for Britain. At the same time, Napoleon saw how it helped Britain. He wanted it stopped. Britain also controlled sugar refining. Napoleon wanted that too.
The demands on the navy, by Britain, were many. There were the Napoleonic Wars (1803-1815). Britain wanted to protect its India project. The navy, of Britain, had to secure trade routes with Cuban and Brazilian slave colonies. African slave trading was more trouble than it was worth by 1807. So, it was stopped, by law.