The corn laws were trade restrictions and tariffs on imported grain and other foods. These laws were enforced in England starting in 1815 after the end of the Napoleonic Wars, and lasted until their repeal in 1846. The Corn Laws benefited landowners and the nobility, who saw substantially increased profits due to lack of foreign competition, and who could often control the vote, as voting rights were not universal at the time. Several movements rose up against the Corn Laws, such as the Anti-Corn Law League, which mobilized the industrial middle classes against the Corn Laws and also aimed to loosen trade restrictions in general. In the end, these movements were successful, and the Corn Laws were repealed in 1846. This repeal was a major decision of the time, and John Stuart Mill would have been well aware of them, especially as he was working in government. As a proponent of free trade, Mill likely supported the repeal of the Corn Laws, which bolstered trade by removing tariffs and other restrictions. Mill would most likely have seen this as a victory and a step towards a more free market.
Sources:
“Corn Law.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., www.britannica.com/event/Corn-Law-British-history.
Britain Express. “The Corn Laws in Victorian England.” Britain Express, www.britainexpress.com/History/victorian/corn-laws.htm.