Rule, regulation (3)
I believe the answer is:
law
I believe this clue is a double definition.
'rule' is the first definition.
(I know that law is a type of rule)
'regulation' is the second definition.
(I've seen this before)
(Other definitions for law that I've seen before include "Rule of conduct" , "Legislation" , "Commandment" , "Set of rules laid down by authority" , "Collection of rules imposed by authority" .)