Since the 1780s, the US legislature has enacted roughly 50,000 laws. Only 33 of these have been proposed amendments to the Constitution, and only 27 of these proposals were passed.
The point is, the overwhelming majority of what government does has nothing to do with the fundamental legal structure of the country. When Islamists talk about implementing Shari’ah, we should bear this in mind. If you establish the Shari’ah as the supreme law of the land in the government’s constitution, still, the vast majority of what the state will deal with on a day to day basis will have little or nothing to do with this. What the issue will be is whether or not the laws and regulations of the government in mundane matters will genuinely reflect Islamic principles and values; and whether or not policy will manifest these principles.
The strictly legal aspect of Islamism is actually quite minimal; because the explicit legal rulings in the Qur’an and Sunnah; the unambiguous, and unanimously agreed upon absolutes that the Shari’ah comprises, are very few.
It is, therefore simply not enough for Islamists to rely upon the call for Shari’ah. We need them to articulate actual policies.