All nations in principle repudiated that trade and Britain made treaties with various maritime powers giving mutual right of search to the naval vessels of each upon the others' merchant vessels.

The African Slave Trade was in fact outlawed for the flags of all nations.

But America, smarting under the memory of impressment injuries, and maintaining in any case the doctrine that in time of peace the national flag protected a vessel from interference or search by the naval vessels of any other power, refused to sign mutual right of search treaties and denied, absolutely, such a right for any cause whatever to Great Britain or to any other nation.
Being refused a treaty, Britain merely renewed her assertion of the right and continued to exercise it.
Thus the right of search in time of peace controversy was not ended with the war of 1812 but remained a constant sore in national relations, for Britain alone used her navy with energy to suppress the slave trade, and the slave traders of all nations sought refuge, when approached by a British naval vessel, under the protection of the American flag.

If Britain respected the flag, and sheered off from search, how could she stop the trade?
If she ignored the flag and on boarding found an innocent American vessel engaged in legal trade, there resulted claims for damages by detention of voyage, and demands by the American Government for apology and reparation.

The real slave trader, seized under the American flag, never protested to the United States, nor claimed American citizenship, for his punishment in American law for engaging in the slave trade was death, while under the law of any other nation it did not exceed imprisonment, fine and loss of his vessel.
Summed up in terms of governmental attitude the British contention was that here was a great international humanitarian object frustrated by an absurd American sensitiveness on a point of honour about the flag.