Timothy Lubin, Washington and Lee School of Law, has published Custom in the Vedic Ritual Codes as an Emergent Legal Principle at 136 Journal of the American Oriental Society 669 (2016). Here is the abstract.
The degree to which the early dharma literature was an extrapolation from the earlier ritual codes can be seen from a number of shared features of form and content. One of these that has not received more than passing notice is the fact that the Dharmaśāstric principle of regarding customary norms as a valid basis of dharma, both in general (sadācāra, śiṣṭācāra) and in limited spheres (deśācāra, grāmadharma, kuladharma, etc.), has its origins in ritual rules in the śrautasūtras and gṛhyasūtras. Passages from the Baudhāyanaśrautasūtra and numerous gṛhyasūtras show that already in these rulebooks established practices of particular social groups were accepted as a valid authority in certain contexts where explicit textual warrant was lacking, and that a further distinction was there made between the general norms of experts and the valid particular norms of locality or social group.Donwload the article from SSRN at the link.