His remarks came on the same day the International Criminal Court handed out its first-ever verdict, convicting a former Congolese warlord of using child soldiers in 2002 and 2003.
But the court faces steep obstacles to tackling alleged atrocities in Syria, now roughly a year into a battered uprising. The reason: Syria has not signed on to join the International Criminal Court.
War crimes could still be prosecuted there if the United Nations Security Council agreed to refer a case, but any of the five countries on the council can block it from doing so. That includes Russia and China, allies of President Bashar Assad that have vetoed action against the Syrian regime in the past.
The apparent stalemate on alleged Syrian war crimes has piqued concern about the limited reach of the International Criminal Court, a relatively new player on the world scene.
"The Syrian situation is frustrating many people," said Leila Sadat, a professor at Washington University School of Law in St. Louis. "It should be at the International Criminal Court. But if two of the powers want to stop it, they can."
Cameron said he knew that Syria was not a part of the International Criminal Court, but he said that Britain was still working to document human rights abuses, sending monitors to the Turkish border to document crimes that “shouldn’t be allowed to stand in our world.”
The prime minister also argued that the West could still appeal to Russia. "It's not in their interest to have this bloodied, broken, brutal regime butchering people nightly on the television screens," he said.
-- Emily Alpert in Los Angeles
Photo: President Obama welcomes British Prime Minister David Cameron during an official arrival ceremony at the South Lawn of the White House in Washington on Wednesday. Credit: Mark Wilson / EPA