This is also what I thought when they issued the warrant against Putin, but it does not seem to be the case. There's a lot of inscrutable legal precedent regarding diplomatic immunity and high crimes, of which there is none higher than genocide. This is exactly why Putin did not make a personal appearance in South Africa for the BRICS summit. South Africa felt that they would be legally obligated to arrest him due to the ICC warrant, and that was all over a far lesser charge of unlawfully deporting children.