The International Criminal Court has begun investigating war crimes in Georgia, is looking into British soldiers accused of torture in Iraq and, in one of its most politically delicate missions yet, sent a team to Israel to discuss crimes in Gaza. But as the court tries to expand into new geography and investigate new types of crimes, it faces the most serious challenge to its existence: Three nations, all from Africa, have announced that they will no longer work with the tribunal, intensifying a longstanding debate over whether it is biased against the continent. In October, Gambia, announced its intention to pull out of the tribunal, denouncing it on state television as the “international Caucasian court.” The planned withdrawal carried an extra barb: Gambia is the home country of the court’s chief prosecutor, Fatou Bensouda. Before that, Burundi announced its plans to withdraw, months after Ms. Bensouda announced that she would open a preliminary examination into the killings of antigovernment protesters there. But most damaging for the court, one of its early champions, South Africa, announced it would leave, too, saying that the court’s writ was “incompatible” with its ability to resolve political conflicts in its neighborhood.