Does the vagueness (ambiguity) of policy making is a good thing or bad thing?

Does the vagueness (ambiguity) of policy making is a good thing or bad thing?

 

Does the vagueness (ambiguity) of policy making is a good thing or bad thing? Should laws say specifically what it is intended to do or should it be open to interpretation as the generations go by? How does ambiguity make policymaking more difficult or does it?