一口通商
Maritime trade with China was banned in 1644 following the Qing conquest under the "Haijin" policies and limited only to Macau on a lesser scale while the new dynasty focused on eliminating surviving Ming loyalists. While the Kangxi Emperor lifted the prohibition in 1684, China again restricted trade under the Canton System in 1757. Foreign ships were required to first stop at Macau before further proceeding to Canton. Qing authorities exercised a much greater role in governing the territory during this period; Chinese residents were subject to Qing courts and new construction had to be approved by the resident mandarin beginning in the 1740s. As the opium trade became more lucrative during the eighteenth century, Macau again became an important stopping point en route to China.