Inherent in the Knesset make up, some form of restrictions, as there is no party that has absolute power. While the laws are came by after many discussions between various intereting parties, members of the coalition. The judiciary is not submitted to such a lengthy dealing and wheeling before giving a decision: it is up to the ideology of the members who are mostly part of the Israeli elite, close to a doctrine more to the left of the majority of the citizenry. As such, there could be more legal derailment in the HCJ than it is a Knesset which is the Legislative power, subject to internal strives and various constituent interests. Sure, a Constitution will allow a set of rules that will delineate any possible derailment from either Power, and there will be no need for restriction as there will be Check and Balance, representing the social, political aspirations of the majority of the population, which is not the current case.
Police disperse hundreds in brawl in Kafr Manda, northern Israel (Haaretz)
from the article: Ex-chief justice signs petition slamming bid to limit court