Although in Dharmaśāstra the ideal person who defines the ācāra of a particular place is dictated as one who knows the Vedas or is “learned”, in actual practice this role is often deferred to group leaders along with Vedic scholars.
[2] Ācāra is theologically important in Hindu law because it is considered, along with the Vedas (Śruti), and Smriti (traditional texts such as the Dharmaśāstra literature), to be one of the sources of dharma.
[7] According to the Mimamsa scholar Kumārila, "when good people act according to certain rules and no motive or goal is apparent in the realm of the observable, then this is to be understood as dharma.
There are a number of telling references to ācāra in Dharmaśāstra texts which reveal the real importance custom had for the settling of legal disputes.
Manu 8.41 likewise states that a judge must study the specific laws practiced by castes (jātidharma), particular regions (janapadharma), and families (kuladharma) before making any legal pronouncements relating to them.
Various scholars hold differing ideas about the origin of the recorded ācāra found in Dharmaśāstra literature such as the Manusmṛti.
Some, such as scholar Richard Lariviere, hold that traditional smṛti texts are "records of actual customs and practices found in classical India".
Various difficult questions arise in regard to the relative force of śruti, smṛti, and ācāra in Hindu law and numerous rules have been laid down in cases of apparent and real conflicts among them.
[13] "Ācāra (customs and usage) are transcendental law, and so are the practices declared in the Veda and the smṛti; therefore a twice-born person desirous of his own welfare should always make effort to follow it.
In the earliest days, ācāra that was to be followed was that observed or declared by learned Brahmins who were highly moral and selfless.