The European war pitting an alliance of monarchies led by Britain against Napoleonic France was a source of immense profits for Americans, who, John Adams quipped, lined their pockets while Europeans slit each others throats. As citizens of a neutral nation, Americans were able to trade with both Britain and France, but such trade encouraged retaliation. Here, John Marshall refers to one form of retaliation: the British practice of "impressment." The British navy, desperate for sailors, claimed the right to stop neutral ships on the high seas, remove seamen alleged to be British subjects, and impress them into the British navy. By 1811, nearly 10,000 American sailors had been forced into the British navy.
The United States therefore require positively, that their seamen who are not British subjects, whether born in America, shall be exempt from impressments. The case of British subjects, whether naturalized or not, is more questionable; but the right even to impress them is denied.