The UK Parliament is continuously evolving. The battle to have power and to use it wisely is a daily one. Constitutional theory may still say Parliament is sovereign, but that is only true if Parliament retains the political will to assert itself.
Parliament gained its supremacy by limiting the power of Kings and then taking over power from the monarch. It retained it by making the institutions of the country bend to its will, reshaping the aristocracy through taxes and changes to the Lords, fashioning regulation and tax for business and the professions, and undertaking a large redistribution of income through the public sector.
In more recent years Parliament has had to rein in the large government it created and sponsored. Even though most government Ministers are also MPs, the Commons has had to use its voices, votes and abilities to prevent the executive using power to excess or taking Parliament for granted under a majoritarian system.
By far and away the largest and as yet unbridled challenge to Parliament’s power has come from the EU. It is true that all the powers the EU possesses were powers that Parliament has granted. A single Act of Parliament could still take back this jurisdiction. However, the longer Parliament leaves a new settlement of powers with the EU the more danger that these powers will eventually be beyond the political power of Parliament to wrestle back. Treaty law is in conflict with Acts of Parliament.
Meanwhile, Parliament has had some successes in recent months and years reminding the executive of its role and supremacy. Ministers’ careers can be broken as well as made in Parliament. The Select Committee system provides a further check on departmental actions and decisions. This Parliament has played a major part in issues like the Syrian war. When no single party has a majority government has to work harder to ensure it has the votes for any measure it wishes to introduce.