There always some users. It was the Chinese governments policy to prohibit trafficing in narcotics.
"The Opium Wars were two wars waged between the Qing dynasty and Western powers in the mid-19th century. The First Opium War, fought in 1839–1842 between the Qing and Great Britain, was triggered by the dynasty's campaign against the opium trade; the Second Opium War was fought between the Qing and Britain and France, 1856–1860. In each war, the European forces used recently developed military technology to defeat the Qing forces, and compelled the government to grant favorable tariffs, trade concessions, and territory.
The wars and the subsequently-imposed treaties weakened the Qing dynasty and Chinese governments, and forced China to open specified treaty ports (especially Shanghai and Guangzhou (Canton)) that handled all trade with imperial powers.[1][2] The resulting concession of Hong Kong after the wars compromised China's territorial sovereignty."
https://en.wikipedia.org/wiki/Opium_Wars
the French were involved 
