During his second term, Jefferson's attention was focused on the trial of then former Vice President Burr for treason, which resulted in an acquittal, and on the issue of slavery, specifically the importation of slaves from abroad. In 1806, he denounced the international slave trade as a 'violation of human rights' and called upon Congress to criminalize it. Congress responded by approving the Act Prohibiting Importation of Slaves the following year. Rising tensions between the United States and Britain dominated the final years of Jefferson's second term, as the Royal Navy began impressing sailors from American ships and attacking American shipping. Jefferson rejected war and instead used economic threats and embargoes that ultimately hurt the U.S. more than Britain. The disputes with Britain continued after Jefferson left office, eventually leading to the War of 1812.