A blockade is a military operation that blocks all maritime movement to or from a port or coast. Blockades may also be aerial. A military operation carried out on land that isolates or encircles an area is called a siege.
A blockade is an act of war that is regulated by international law—namely, by the 1856 Paris Declaration Respecting Maritime Law and by Articles 1–22 of the 1909 London Declaration Concerning the Laws of Naval War. It is important to distinguish between the terms blockade and embargo . An embargo is a type of economic sanction that may be adopted under the aegis of the UN or another international organization, to try to force a State to comply with a decision.
Regardless of whether the situation is a blockade or an embargo, humanitarian law clearly posits that States are under the obligation to allow the free passage of relief that is of an exclusively humanitarian and impartial nature and is indispensable to the survival of the civilian population (GCIV Art. 23, API Art. 70, and APII Art. 18.2).
For Additional Information: Dinstein, Yoram. The Conduct of Hostilities under the Law of International Armed Conflict . Cambridge: Cambridge University Press, 2004, esp. 104–6.
Heintschel von Heinegg, Wolf. “The Law of Armed Conflict at Sea.” In The Handbook of Humanitarian Law in Armed Conflict , 470–73. Oxford: Oxford University Press, 1995.