 During this time, the social and moral code of Shabdrung Ngawang Namgyal evolved to a code of regulations for the unified Kingdom of Bhutan.Many basic tenets of the Bhutanese Tsa Yig live on in modern legal codes, including its Constitution.The Tsa Yig of Shabdrung Ngawang Namgyal laid down the dual system of government of Bhutan, a synthesis of spiritual and temporal authority.