Related Rule
Practice Relating to Rule 29. Medical Transports
Section C. Respect for and protection of hospital ships
In the Dover Castle case in 1921, a German court acquitted the commander of a German submarine of sinking a hospital ship and killing six members of its crew in violation of the customs and laws of war. The Court found that the commander had sunk the ship in execution of orders and could not, therefore, be held responsible for the ensuing violations of the law. 
Germany, Reichsgericht, Dover Castle case, Judgment, 4 June 1921, p. 429.
In 1944, the German hospital ship the Tübingen was bombed and sunk by the British air force. Following the sinking, the German Government issued the following official protest:
On 18 November 1944 at 0745 hours near Pola the German hospital ship Tübingen was attacked by two double-engine British bombers with machine guns and bombs so that it sank, although the course of the hospital ship had been communicated to the British government well in advance of its voyage to Saloniki and back for the purpose of transporting wounded German soldiers. Numerous members of the crew were thereby killed and wounded. The German government emphatically protests the serious violations of international law committed by the sinking of the hospital ship Tübingen. 
Germany, as cited by Alfred M. de Zayas, The Wehrmacht War Crimes Bureau, 1939–1945, University of Nebraska Press, Lincoln, 1989, pp. 261–266.