Related Rule
Germany
Practice Relating to Rule 33. Personnel and Objects Involved in a Peacekeeping Mission
Germany’s Military Manual (1992) states:
When a United Nations’ force or mission performs functions of peacekeeping, observation or similar functions, each party to the conflict shall, if requested … take such measures as may be necessary to protect the force or mission while carrying out its duties … The protection of the force or mission shall always be ensured. 
Germany, Humanitarian Law in Armed Conflicts – Manual, DSK VV207320067, edited by The Federal Ministry of Defence of the Federal Republic of Germany, VR II 3, August 1992, English translation of ZDv 15/2, Humanitäres Völkerrecht in bewaffneten KonfliktenHandbuch, August 1992, § 418.
Germany’s Law Introducing the International Crimes Code (2002) punishes anyone who, in connection with an international or a non-international armed conflict,
directs an attack against personnel, installations, material, units or vehicles involved in a … peace-keeping mission in accordance with the Charter of the United Nations, as long as they are entitled to the protection given to civilians or civilian objects under international humanitarian law. 
Germany, Law Introducing the International Crimes Code, 2002, Article 1, § 10(1)(1).
In 1995, during a debate in the UN Security Council, Germany condemned attacks against UNPROFOR. 
Germany, Statement before the UN Security Council, UN Doc. S/PV.3553, 12 July 1995, p. 11.