Legal precedents exist, because laws are interpreted / combined, deduced. Sure, it is not regulatory or statutory law (executive and legislative branches). Yet,

Legal precedents exist, because laws are interpreted / combined, deduced. Sure, it is not regulatory or statutory law (executive and legislative branches). Yet, courts (and police etc) are bound by the rule of stare decisis. Namely, a court has to abide and be consistent with rulings of higher courts. For instance, if a court says abortion is legal, lower courts, police, and the affected governments (e.g. states, municipalities) have to abide to that ruling/case law. In other systems, if a law leads to contradiction, or is lacking clarity, the court applies specific 'procedures' to solve the issue (e.g. a law can be ruled unconstitutional or void). Here, the court decides on the details to produce a "reasonable" law. Edit: But yes, you are right: unlike the legislative branch a court may not propose an arbitrary law (they can advise/make suggestions to the legislative branch).