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Copyright use to have similar sense (must apply, must renew).

Ah, this is mostly the tension between "balancing tests" and "bright-line rules" in jurisprudence. I worked in criminal law for a while, and it's basically statutory, which means mostly bright line rules for prosecution. Sentencing involves more balancing tests, that's probably what you're thinking about. Though there are even some mandatory minimums that are bright lines.

One of the balancing tests you hear about the most is actually in IP law, the fair use standard. (People sometimes casually talk about fair use as if it's a list of four bright line criteria, but that's not really correct.)

Bright line rules are handy in that they add clarity for everyone following the law. Businesses that want to establish processes in explicit compliance tend to prefer bright lines, for example. Balancing tests are important when you're safeguarding the rights of the people against the state, or when individual cases will have unique mitigating circumstances that are too numerous to foresee or account for in a hard and fast rule. Balancing tests help add lenience, or help customize the law to particular situations. That's why you might see more balancing tests in sentencing, or in constitutional issues.

UPDATE: Statutes also tend to be more bright-line, while traditionally, judges made common law with more balancing tests. The US (thanks to the UK) is considered a common law jurisdiction, since we have some judge made law, while most European courts are said to rely on civil code. This is oversimplistic though, because these days European judges are more willing to look at precedents and adopt customs based on prior cases, and many US jurisdictions have implemented "uniform codes" which attempt to codify many areas of the law formerly left to judges. Everyone's a bit of a blend now, just with more of a common law or civil law flavor. (Pending correction from any European Advocates out there, of course.) Moreover, some judges develop bright lines, and some statutes call for fairness tests, so it's all blurred now.