Abstract: In many constitutional regimes, constitutional powers atrophy over time. Examples of atrophied powers include the royal veto in the UK, the power of the Canadian federal government to ‘disallow’ provincial laws, the power of the US Congress to expand the number of Supreme Court justices (‘court-packing’), the ‘notwithstanding clause’ that authorizes the Canadian Parliament to override judicial decisions, and congressional impeachment of executive officers. This article offers mid-level hypotheses about the atrophy phenomenon. A power that is not exercised tends, over time, to become unexercisable. When a power goes unexercised over some sufficiently long period, its use comes to seem illegitimate to boundedly informed publics. Such publics use a political precedent heuristic, according to which an attempt to revive the power at a later time amounts to an illegitimate attempt to change the rules of the political game. Accordingly, constitutional actors who wish to prevent the atrophy of particular constitutional powers would do well to engage in pointless exercises of power—a form of deliberate precedent-setting in which the power is exercised merely to preserve its existence for the future. The main illustration involves legislative power to overturn or override constitutional or quasi-constitutional decisions of the judiciary, with special reference to judicial review under the Human Rights Act in the UK.