Complex sentence: All the parlements could issue regulatory decrees for the application of royal edicts or of customary practices; they could also refuse to register laws that they adjudged as either untimely or contrary to the local customary law (and there were 300 customary law jurisdictions).
Split into simpler sentences: All the parlements could issue regulatory decrees for the application of royal edicts or of customary practices. They could also refuse to register laws that they adjudged as either untimely or contrary to the local customary law (and there were 300 customary law jurisdictions).