This has been tried and failed multiple times..
-Weimar Germany (1919-1933)
-Antebellum American South (1800s-1861)
-Münster Anabaptist Kingdom (1534-1535)
-Roman Republic (1st century BC)
When culture becomes the ultimate authority for law, you get no external check on cultural drift toward injustice, oppression, or self destruction. Culture can embrace terrible things and when law simply follows culture, there’s no mechanism for correction.