A legislature or a judiciary are still the government. I use the term to refer to the whole mechanism, not just an executive.

Regardless of where they derive their power from (democracy, monarchy, whatever). Constitutions exist to provide limits on even the power of the current majority to change fundamental aspects of governance. The U.S. Constitution for example, requires a very high bar before alterations can be made, precisely to avoid even democratically-elected representatives from making changes, even where those changes would enjoy popular support.