Legal-Normative regenerability. This is the degree to which an established legal norm, if put through the process of being proposed again as a law, would enjoy broad enough support to be reauthorised.
Sometimes things are marked as foundational in a governmental system, given a certain amount of protection from the needs of the time. They might be written into foundational or monumental documents (the current constitution of a country, the Magna Carta, or so on) in a way that makes repealing/replacing them difficult. There are also laws and institutions that don't come from the normal legislative process of a country, particularly in common law systems where the courts have long had a limited creative power.
Sometimes they're just laws/institutions but are difficult to touch politically even if proposing them anew might not succeed; the political football combined with human psychology contribute to this. It's harder to publicly justify taking something away than leaving it, but also hard in modern American discourse to justify establishing new public services.
On the other end, particularly troublesome laws can sometimes get additional approval by having sunset clauses, requiring reauthorisation or reproposal after a certain period of time. Likewise, in the United States the executive branch has reasonable discretion in issuing executive orders to shape policy, using its discretion in its control over its own branch of government to temporarily restructure itself (until the next president comes in, which can undo anything done this way with the stroke of a pen).
Sometimes legal-normative regenerability can be broadly lower by the features of debate in the system; legislation can be delayed forever or discussion can be cut short in some legal systems. Were we to start again with just our foundational documents and the common law traditions, or even more basically with just a rudamentary system for voting and nothing else, how much of the way we do things nowadays would be regenerated as legal norms? Would we even be able to form a workable society given our current differences?
In some ways this might be positive; there are areas of institutional corruption that might be cleared by a fresh slate. We might manage to avoid our current form of farm subsidies were it to come to a fresh vote without expected continuation. Still, weaving things into the status quo is a powerful thing.