Colombian President Ivan Duque said Sunday he objects to several articles in legislation implementing a 2016 ceasefire agreement with the Revolutionary Armed Forces of Colombia (FARC) rebel group, ignoring warnings by supporters of peace and the International Criminal Court (ICC).

Duque objected to six of the 159 articles in the so-called Special Jurisdiction for Peace (JEP), which established a tribunal to investigate, judge and sentence those considered responsible for crimes during a five-decade war with the government. The agreement, entered into in 2016, put an end to the FARC’s role in a conflict that killed 260,000 people and displaced nearly 7 millions.

Duque’s action is highly controversial, and is seen as a blow to the country’s peace process. Duque is likely to face a major backlash from both the legislative and judicial branch since both congress and the constitutional court had already approved the JEP. The ICC hinted last month that it could proceed to investigate alleged state war criminals if Duque decided to further frustrate the war crimes tribunal.