Blockades restrict the trading rights of neutrals, who must submit for inspection for contraband, which the blockading power may define narrowly or broadly, sometimes including food and medicine. ... Close patrol of hostile ports, in order to prevent naval forces from putting to sea, is also referred to as a blockade.

What do blockades do?

In a memorandum prepared for the London Naval Conference of 1908–09, the British government defined a blockade as “an act of war carried out by the warships of a belligerent, detailed to prevent access to or departure from a defined part of the enemy's coast.” This differs from a so-called pacific blockade inasmuch as ...

Are naval blockades legal?

Naval blockades are acts of war under international law, so one country may legally blockade another only if it is acting in individual or collective self-defense—the standard requirements for going to war—or the U.N. Security Council has proclaimed the action necessary to maintain international peace.