Related Rule
El Salvador
Practice Relating to Rule 64. Conclusion of an Agreement to Suspend Combat with the Intention of Attacking by Surprise the Adversary Relying on It
El Salvador’s Code of Military Justice (1934) punishes any “soldier who … violates a truce, armistice, capitulation or other agreement concluded with the enemy”. 
El Salvador, Code of Military Justice, 1934, Article 67.
El Salvador’s Penal Code (1997), as amended to 2008, which contains a section on the violations of the laws or customs of war, states:
Anyone who violates treaties concluded with foreign States, truces or armistices agreed between El Salvador and an enemy State or between its warring factions, or a duly issued laissez-passer, will be sanctioned with one to three years of prison and a special disqualification from the exercise of his or her function or employment for the same length of time. 
El Salvador, Penal Code, 1997, as amended to 2008, Article 359.