Legalist

noun

1. One who practises or inculcates strict adherence to law; specifically, in theology, one who regards conformity to the law as the ground of salvation, or who is rigorous in exacting obedience to the letter of the law.
2. One who practices or advocates strict conformity to law; in theology, one who holds to the law of works. See legal, 2 (a).
3. One who adheres to legalism.