Maybe the "unwritten" constitution of the UK is, ironically, more stable than ours. Here, power of a few to "interpret" underlying text can instantly collapse decades of precedent built upon it. There, Parliament can act radically but all precedent they don't take a scalpel to remains underneath.

If U.S. Marshals, being the oldest law enforcement agency, never had any of their original authorities specifically limited by modern statutes, they might still be able to instantly deputize basically anybody.