Especially in relation to the United Kingdom around 1722 (as there was no war fought to make the industry as obviously risky for those engaged in it unlike the US), but also in relation to new African Slaves introduced in 1865 to the US.

The thought occurred to me while researching the history of Liverpool (wealth in the 18th / 19th century built primarily on the slave trade). When I came across the Slave Trade Act I thought there must have been ships who left before the act of parliament was signed off and arrived with a ship full of what would unexpectedly be 'free men'. The Slave Trade was hotly debated for years, but the pro lobby had enough support to put (by the sounds of it) a reasonable amount of doubt on the passing of any potential Act in the minds of those engaged in the Trade.