Here, I’ll give an analogy. Sharia law is very similar to Common law in many ways.
One of which is case-law. Jurisprudence is important in Sharia law as it is in Common law and in both judges have a lot of leeway in interpreting law.
New interpretations of law are effectively “new laws”, which is how they create law.
fiqh in Sharia isn’t quite as powerful as stare decisis in common law; share decisis is binding whereas fiqh has slightly less authority. But it serves a similar function .