Israel's involvement would actually let Assad off the hook. No doubt Israel is such a pariah in the Arab world that its involvement could easily trigger a Pan Arab response. Its simply too risky for the Israeli people despite the absolute horror of Syrian civilians. Were Arab countries of the Arab league do the unthinkable and ask Israel to get involved, then that would be a different matter. It won't happen because as Israelis are found of saying, sadly Arabs hate Jews more than they love their own.
World Jewish Congress: Nazi train treasures must go to rightful owners (Reuters)