If Assad had been overthrown and was in custody, and it was decided not to put him in the dock, that would be letting him off the hook. But he hasn't been overthrown, and he's not in custody.

I''m not suggesting he shouldn't be put on trial. I'm saying that negotiations should be without preconditions. That includes insisting that before anything can be done Assad will be removed or his removal will have been agreed by the Syrian government.

Peace in Vietnam wasn't put on hold until Nixon annd Kissinger and co were put on trial. Sometimes you have to accept it that justice might neve be done. Most times in fact.