The question with Arafat wouldn't be whether he was prime minister or whatever, it would be whether he was in fact in a position to control and stop violence that amounted to war crimes.

Sharon managed to avoid getting tried for the massacres in Lebanon, on the grounds that, though he was in chrge of the miliart operation, he wasn't in fact in full control of what his agents did in Sabra and Shatilla. In Qibya in 1953, where his men killed scores of civilians in an attack on a village that involved blowing up houses, the excuse was, I gather, that they didn't actually know there were people in the houses... Unfortunately perhaps it never ever went to trial in either case, which might have cleared up a lot of things.

I'd like to see them both in the dock in some neutral country. Maybe they'd even get cleared. Being put on trial should have nothing at all to do with whether your side wins or not. If you pull off a successful bank raid, that isn't normally seen as a reason you shouldn't be tried for it, so why should it be different for politicians and generals and other public servants?