This person is called a "law abiding citizen."

Hello Hasan: I think the term you are looking for is something like "lawful". They are "lawful" people, or people who "follow the rule of law". The opposite would be an indication that the people are "lawless" or engage in "lawlessness". However, you may be seeking for another word in a slightly different context. The study of law, in the context of legal scholarship, is termed "Jurisprudence". For example, American Jurisprudence pertains to those legal conceptions which are used in the formulation of laws. Other countries have their own Jurisprudence. In yet another context, you may be searching for a term like "Legalism" which refers to the invocation of laws as a strict guide to behavior, etc. I hope this helps. . .