What you need to know:
- A total of 123 countries have ratified the court's founding Rome Statute, meaning they recognise its jurisdiction, but there are some conspicuous absences, notably the United States, Russia and Israel.
- Russia's invasion of Ukraine has vaulted the former Soviet state to the top of the agenda of a court often accused of unfairly focusing on Africa. Four days after the war started ICC prosecutor Karim Khan announced an investigation into possible war crimes.
The International Criminal Court, which celebrates its 20th anniversary on July 1, is the world's only permanent tribunal to investigate and try alleged cases of genocide, war crimes, crimes against humanity and aggression where member states are unable or unwillling to do so.
Here are five things to know about the court based in the Dutch city of The Hague, which is investigating alleged war crimes in Ukraine.
US, Russia, Israel opted out
A total of 123 countries have ratified the court's founding Rome Statute, meaning they recognise its jurisdiction, but there are some conspicuous absences, notably the United States, Russia and Israel.
Both the United States and Russia have signed the Rome treaty but never ratified it. Moscow in 2016 withdrew its signature over an ICC report calling its annexation of the Crimean peninsula an occupation.
Israel opposed the court from the outset, fearing that its leaders and/or military could be targeted in politically motivated cases.
Other notable non-members include China, India and Myanmar.
The ICC can pursue nationals of non-member states for crimes committed on the soil of a member country or, as in the case of Ukraine, a non-member that recognises its jurisdiction.
The UN Security Council can also call on the court to investigate potentially serious international crimes, as for instance in Libya and Sudan.
Five convictions in two decades
Between 2012 and 2021, the ICC successfully convicted five men of war crimes and crimes against humanity, all Africans.
Three of the five were former militia leaders from the war-torn Democratic Republic of Congo, with Bosco Ntaganda, a rebel leader nicknamed "Terminator" receiving the longest jail sentence the court has issued of 30 years for mass murder, rape and abduction.
The court also sent Dominic Ongwen, a commander of Uganda's notorious Lord's Resistance Army militia to jail as well as Malian jihadist Ahmad al Faqi al Mahdi, who was convicted of destroying a mosque and mausoleums in the ancient Malian city of Timbuktu.
Former Ivory Coast president Laurent Gbagbo was the first former head of state to be tried by the ICC in 2016 but he was acquitted of crimes against humanity.
Some convictions were overturned on appeal, notably that of former Congolese vice-president Jean-Pierre Bemba, who was convicted of crimes committed by rebels under his command in Central African Republic but later cleared of responsibility.
Failures and fugitives
The court suffered a major setback in 2014 when its highest profile case -- over Kenyan President Uhuru Kenyatta's involvement in the inter-ethnic violence that broke out after disputed 2007 elections -- collapsed.
Kenyatta reluctantly appeared before the court, the first sitting head of state to do so, but the prosecutor was forced to drop the case amid allegations of witness intimidation and bribery.
Former Sudanese president Omar al-Bashir is also still being wanted by the ICC for genocide, crimes against humanity and war crimes in the western Sudanese province of Darfur. But three years after he was deposed Sudan has yet to hand him over.
The son of former Libyan leader Moamer Kadhafi, Seif al-Islam Kadhafi, has been wanted by the court on war crimes charges for over a decade.
Dispute with Trump
The ICC infuriated US president Donald Trump's administration in March 2020 by authorising an investigation into alleged war crimes by US forces serving in Afghanistan.
Washington imposed sanctions on the ICC's prosecutor in protest but his successor Joe Biden later lifted them.
The investigation, which also included violence by the Taliban and Islamic State (IS) group, was later suspended at the Afghan government's request but relaunched after the Taliban takeover.
Since it resumed however, it has focused on violence by the Taliban and IS to the exclusion of alleged US atrocities.
Pivot to Ukraine
Russia's invasion of Ukraine has vaulted the former Soviet state to the top of the agenda of a court often accused of unfairly focusing on Africa. Four days after the war started ICC prosecutor Karim Khan announced an investigation into possible war crimes.
Ukraine is not an ICC member either but it has accepted the court's jurisdiction.
A 42-strong team of ICC investigators visited Ukraine in May to gather evidence and Khan visited the Kyiv suburb of Bucha, where dozens of civilians were found murdered after the withdrawal of Russian troops.