In a historic ruling, the International Criminal Court has opened the door to potential war crimes charges against members of the United States Armed Forces, the Taliban and other combatants in Afghanistan's armed conflict.

A decision by the courts pre-trial chamber reverses an earlier ruling and could cover investigations into alleged crimes by the Taliban but will also investigate an alleged program of torture conducted by the U.S. military, the CIA and the Afghan National Security Forces.

Presiding Judge Piotr Hofmanski said in his ruling: "The appeals chamber considers it appropriate to...authorize the investigation."

U.S. Secretary of State Mike Pompeo reacted angrily to the ruling, calling the ICC "an unaccountable political institution, masquerading as a legal body." 

He also said the timing of the investigation is "reckless," coming just as U.S. and the Taliban try to save their March 1 peace agreement to end a near two-decade long conflict—the longest war in U.S. history.

Of all the entities created by the United Nations the International Criminal Court is perhaps the most ambitious and contentious.

Set up in 2002 with the aim of trying individuals accused of genocide, crimes against humanity, war crimes and the crime of aggression, the ICC was meant to step in when national courts could not, or would not. 

But from its inception, the ICC has been dogged by accusations of infringing on national sovereignty, bias and targeting poor, unstable countries rather than rich, western ones.

The court has 123 member states. The U.S., China, India, and Israel did not join. Its statutes claim international law has precedence over national sovereignty in some cases, which can provoke outrage. 

The Russian Federation withdrew from the ICC after a UN committee condemned alleged human rights violations in Crimea. Philippines President Rodrigo Duterte called the tribunal "useless," withdrawing Philippines from the ICC in 2019 after the court opened an investigation over alleged crimes against humanity during Duterte's drug war.

The court so far has launched cases primarily against African leaders, including former Sudanese President Omar al-Bashir, Kenyan President Uhuru Kenyatta, Libyan leader Muammar Gaddafi, Côte d'Ivoire  President Laurent Gbagbo, and Democratic Republic of Congo Vice President Jean-Pierre Bemba. 

The United States has even backed some of these cases.