In a stiff blow to the government, Colombia's highest court for constitutional questions on Wednesday struck down an expansion of the military justice system that human rights activists had said would lead to greater impunity for war criminals.

In a 5-4 decision not subject to appeal, the Constitutional Court nullified a constitutional amendment and pursuant statute that would have placed under the jurisdiction of an expanded military justice system all but seven types of violations of international humanitarian law involving armed forces personnel.

Currently, all human rights cases are supposed to be tried in civil court.

Magistrate Jorge Ivan Palacio read a statement saying the court found "procedural defects" in the change's journey through Congress, accepting the arguments of opposition lawmakers and a top human rights lawyer. The decision was not released.

Defense Minister Juan Carlos Pinzon called the ruling "a blow to the morale of the military forces that without doubt will affect Colombians' security." He said the government would consider submitting a revised military court overhaul, but gave no details.

President Juan Manuel Santos was seen as having pushed the change through Congress to win the backing of military leaders for peace talks that began last year with the country's main rebel group in Cuba.

Santos repeatedly insisted the legal change would not lead to impunity in war crimes, but such arguments did not persuade members of the U.S. Congress, which withheld at least $10 million in military aid in objection to the measure.