This article analyzes the contribution of the Guidelines for the Implementation of the 1999 Second Protocol to the Hague Convention of 1954 for the Protection of Cultural Property in the Event of Armed Conflict (the Guidelines) to better protection of cultural property in peacetime and in times of armed conflict. The first part of the article introduces the Guidelines within the context of the implementation of the 1999 Second Protocol to the Hague Convention of 1954 for the Protection of Cultural Property in the Event of Armed Conflict (1999 Second Protocol) and the 1954 Hague Convention for the Protection of Cultural Property in the Event of Armed Conflict, and provides examples of UNESCO's other standard-setting instruments such as the 1972 Convention Concerning the Protection of the World Cultural or Natural Heritage, the 2001 Convention on the Protection of the Underwater Cultural Heritage and the 2003 Convention for the Safeguarding of the Intangible Cultural Heritage, as well as bodies providing for guidelines for these instruments. The second part underscores the most important advances of the Guidelines in the implementation of the 1999 Second Protocol. The third part focuses on the contribution of the Guidelines as subsequent practice in the application of the 1999 Second Protocol establishing the agreement of the parties regarding its interpretation in the framework of Article 31(3)(b) of the 1969 Vienna Convention on the Law of Treaties. Finally, the fourth part concludes by highlighting the main advantages of the Guidelines in providing better protection for cultural property.