Customs Consolidation Act, 1853

Her Majesty, by Order in Council, may impose restrictions on ships of a foreign country in certain cases;

324. If it shall be made to appear to her Majesty that British vessels are subject in any foreign country to any prohibitions or restrictions as to the voyages in which they may engage, or as to the articles which they may import into or export from such country, it shall be lawful for her Majesty (if she think fit), by Order in Council, to impose such prohibitions or restrictions upon the ships of such foreign country, either as to the voyages in which they may engage or as to the articles which they may import into or export from any part of the United Kingdom or of any British possession in any part of the world, as her Majesty may think fit, so as to place the ships of such country on as nearly as possible the same footing in British ports as that on which British ships are placed in the ports of such country.