Primary law has “mandatory authority” (or “binding authority”) when they are from the same governing jurisdiction or a higher court. Other primary sources from outside a given jurisdiction only have what’s called “persuasive authority,” which is non-binding.
Secondary sources are non-binding and never mandatory authority, but their persuasiveness can vary. Courts may choose to follow persuasive authority, but they are never obligated to do so. Persuasive authority is never binding on a court, but you can consider citing to persuasive authority if no mandatory authority exists, or if you want to add more support to the mandatory authority you’ve cited.
Understanding which resources are authoritative can be confusing. If you feel unsure in this area or want to check your understanding, this visual overview may help. The pyramid provides examples of the types of authority listed on the left. Make sure to read the notes on either side of the pyramid.