BY MELISSA JORDON – Seventy-five years ago today, unlimited submarine warfare commenced as German U-boats began sinking passenger liners. While the first ideas to build submarines came centuries before, the first steam-powered naval submarine was built by an American for the U.S. Navy in 1875.
A look into the development of law of the seas and laws of submarine warfare shows that while some improvements have been made, we are still left without much guidance or legal answers to questions governing submarine warfare. This article examines the development of relative laws of the seas and laws governing naval warfare to examine the changes and discussions that have resulted from the abuses of international law conducted under submarine warfare and the changes of what is acceptable practice under international principles today.
The role of submarines in naval warfare was not taken seriously or addressed until the intervals between WWI and WWII. At the end of the 19th century, naval warfare consisted mainly of gunfire between surface ships, controlling maritime commerce, and blockades. Great Britain’s navy controlled the seas throughout much of this time, and it remained unconcerned with submarines, believing its own escorts and convoys would be able to subdue any submarines on the high seas.
With Great Britain’s naval power, came a lot of influence over the international law and customs governing the seas. The 1909 London Protocol, made in conjunction with the Geneva Convention of 1907—establishing the prize court—was attended by 10 of the powerful nations and called for rules governing blockades, contraband, and capture of or destruction of neutral vessels. While this protocol never entered into force, several belligerents respected it during WWI as international prize law. The relevant part of the protocol stated:
“Article L: Before the vessel is destroyed all persons on board must be placed in safety, and all the ship’s papers and other documents which the parties interested consider relevant for the purpose of deciding on the validity of the capture must be taken on board the ship.” 
The issue of submarine warfare came front and center during WWI, primarily towards attacking merchant ships. Germany’s declaration of a war zone around the British Isles, stating that enemy merchant ships would be attacked in that zone without warning, led to a German submarine sinking of the LUSITANIA (with over 100 Americans on board) in 1915. Germany justified her actions as retaliation to Great Britain’s illegality (claiming the entire North Sea as a military zone, laying a Mine Barrage, and its attempt to stifle neutral trade shipping food to Germany). However, in response to the United States’ protest and denunciation of Germany’s actions, Germany acknowledged liability, offered reparations, and stated that they would act in accordance with the general principles recognized by international law to not sink merchant vessels without saving human lives, whether within naval warzones or not.
This did not last long, and Germany, without repudiating its statement, resumed unrestricted submarine warfare in 1917, again in retaliation to Great Britain’s ruses of flying different flags, arming merchant vessels to attack, and making identification difficult. At the end of WWI it appeared submarine’s were treated the same as surface warships, and were supposed to warn before sinking, which for the most part was observed and respected until 1917.
In between the wars, an additional protocol, the 1936 London Submarine Protocol—supplementing the 1930 London Treaty that expired— article 22 governing the law of submarines remained in effect without a time limit. It stated:
“Except in the case of persistent refusal to stop on being duly summoned, or of active resistance to visit or search, a warship, whether surface or submarine, may not sink or render incapable of navigation a merchant vessel without having first placed passengers, crew, and ship’s papers in a place of safety….”
The protocol was accepted by over 40 countries at the time, further enforcing the rule as a custom of international law, however, during WWII, it was disobeyed by not only Germany in response to the same British-German retaliation, but also the United States against Japan. In the aftermath of WWII, the tribunal at Nuremberg found that the protocol still formed a part of international law of submarine warfare, yet the limits of submarine warfare remained unclear as the court held, sinking a merchant ship was not a punishable crime when the victorious side was found to use similar action.
What came from the unrestricted submarine warfare that led to several merchant ships and innocent civilians under attack? Changes came slowly from individual state initiatives and publications of their own manuals, like the U.S. Navy’s 1995 manual for The Law of Naval Warfare and from the United Nations. The United Nations rules limiting the threat or use of force govern some of the laws that would concern naval warfare, but it took almost 40 years after the last war to solidify and make clear the boundaries and rules governing the sea in general. This came to fruition in 1982 with the United Nations Convention on the Law of the Sea (LOS), providing for large expansions in states’ territorial seas, establishing exclusive economic zones and the rights guaranteed to the coastal state and regulates the behaviors of states entering into these zones and waters. The LOS does not give extensive guidance in dealing with warships, however it does provide for cases where ships may be arrested, warships may be detained, and require submarines to surface while travelling within the coastal state’s territorial sea.
While the LOS provides some guidance, it is more concerned with environmental and resource protections developed states were eager to get at and undeveloped states were eager to limit and protect. Rather, the 1995, the San Remo Manual on International Law Applicable to Armed Conflicts at Sea. This manual was written by several naval experts through roundtables, provides a contemporary restatement of laws applicable to armed conflict. It provides for categories of ships exempt from attack, not conducting hostilities in eco-protected marine areas, criteria to determine whether a merchant vessel should be considered a military vessel subject to attack, changing rules and regulations for blockades, etc.
Today, more than 60 years after the last World War, we are left with some basic principles and guidance towards submarine warfare and laws governing the seas. Much of the law developed over the past century has long been recognized as customary international law. How submarine warfare is carried on from here on will continue to have to be considered in combination with UN treaties and other laws governing warfare as states have been hesitant to agree and set down in writing the laws governing submarine warfare. The principles of the 1936 protocol remain relevant even today, but adherence to these general principles and customs is still uncertain.
 German U-Boat, Sinking of SS Athenia, uboataces.com, (Nov. 13, 2014), http://www.uboataces.com/boa-opening.shtml.
 Submarine Development, U.S. Navy Museum, (November 15, 2014) http://www.history.navy.mil/branches/teach/dive/hist1.htm
 Ashley J Roach, et. al., SYMPOSIUM: THE HEAGUE PEACE CONFERENCES: The Law of Naval Warfare at the Turn of Two Centuries, 94 A.J.I.L. 64, 64 (2000). [Hereinafter Roach, Law of Naval Warfare at the Turn of Two Centuries].
 Both the 1909 and 1936 protocols on naval warfare were held in London.
 Roach, Law of Naval Warfare at the Turn of Two Centuries, at 65.
Final Protocol to the Naval Conference of London, 208 Consol. T.S. 338 (1909)
 Lieutenant Horace B. Robertson, Jr., Submarine Warfare, 1956 JAG J. 3, at 4 ( 1956).
 Id. at 4.
 Id. at 5.
 Id. at 5, citing Proces-Verbal Relating to the Rules of Submarine Warfare Set Forth in Part IV of the Treaty of London of 22 April 1930, signed at London, November 6, 1936.
 Lieutenant Horace B. Robertson, Jr., Submarine Warfare, at 6.
 Id. at 7.
Roach, Law of Naval Warfare at the Turn of Two Centuries, at 65.
 United Nations Convention on the Law of the Sea, opened for signature Dec. 10, 1982, 1833 U.N.T.S. 397.
 Id. at Art. 20
 ICRC, “San Remo Manual on International Law Applicable to Armed Conflicts at Sea, 12 June 1994,” International Committee of the Red Cross, (November 15, 2014), https://www.icrc.org/ihl/INTRO/560?OpenDocument.
 Roach, Law of Naval Warfare at the Turn of Two Centuries, at 65-71.