According to the Vedic sastras, everything must be done according to regulative principles, but here it is stated that the thieves and rogues devised their own process for killing an animalistic man
SB Canto 5
After this, all the thieves, according to their imaginative ritual for killing animalistic men, bathed Jaḍa Bharata, dressed him in new clothes, decorated him with ornaments befitting an animal, smeared his body with scented oils and decorated him with tilaka, sandalwood pulp and garlands. They fed him sumptuously and then brought him before the goddess Kālī, offering her incense, lamps, garlands, parched grain, newly grown twigs, sprouts, fruits and flowers. In this way they worshiped the deity before killing the man-animal, and they vibrated songs and prayers and played drums and bugles. Jaḍa Bharata was then made to sit down before the deity.
In this verse the word sva-vidhinā (according to their own ritualistic principles) is very significant. According to the Vedic śāstras, everything must be done according to regulative principles, but here it is stated that the thieves and rogues devised their own process for killing an animalistic man. The tamasic śāstras give instructions for the sacrifice of an animal like a goat or buffalo before the goddess Kālī, but there is no mention of killing a man, however dull he may be. This process was manufactured by the dacoits themselves; therefore the word sva-vidhinā is used. Even at this time there are many sacrifices being conducted without reference to the Vedic scriptures. For instance, in Calcutta recently a slaughterhouse was being advertised as a temple of the goddess Kālī. Meat-eaters foolishly purchase meat from such shops, thinking it different from ordinary meat and taking it to be the prasāda of goddess Kālī. The sacrifice of a goat or a similar animal before the goddess Kālī is mentioned in śāstras just to keep people from eating slaughterhouse meat and becoming responsible for the killing of animals. The conditioned soul has a natural tendency toward sex and meat-eating; consequently the śāstras grant them some concessions. Actually the śāstras aim at putting an end to these abominable activities, but they impart some regulative principles so that gradually meat-eaters and sex hunters will be rectified.