The Śyena sacrifice is a sacrifice aiming at the death of one’s enemy. The usual interpretation of the Śyena sacrifice is that you just don’t perform it, because it is violent and violence is prohibited (unless it is performed as an element of a rite, e.g., in the Agnīṣomīya). Here comes, however, a novel interpretation:
“For Mīmāṃsā, it is not the case that violence in itself is the cause for pāpa (evil karman), only prohibited violence is. The killing of the sacrificial animal performed within the Jyotiṣṭoma is [just] effecting that the sacrifice is complete with all its elements.
Out of the result of the Śyena sacrifice anartha is produced. Out of this result, which consists in the killing of one’s enemy, there is anartha in the form o reaching suffering, i.e., hell. [For] the killing of one’s enemy, which is the result of the Śyena sacrifice, is not known through a prescription. However, If the enemy is already ready to kill (ātatāyin), then his killing is prescribed. Since in that case violence is prescribed, the Śyena sacrifice does not produce anartha. Therefore, it is established that the Śyena sacrifice does not in itself lead to anartha as result.”
(p. 25 of Rāmaśaṅkara Bhaṭṭācārya’s commentary (called Jyotiṣmatī) on Sāṃkhyatattvakaumudī)
The author of this work, Dr. Ram Shankar Bhattacharya (1927-1996), was a scholar of international repute, well-known for his ground-breaking works in the field of Indological scholarship in general and Sanskrit in particular. He was a pupil of Hariharānanda Āraṇya and then of his successor, Dharmamegha Āraṇya. He has at least 30 works and hundreds of articles in various languages (English, Bengali, Hindi and Sanskrit) dealing with Purāṇas, Sānkhya and Yoga philosophies, Sanskrit grammar, Indian History, etc. to his credit. He co-edited (along with Prof. Gerald James Larson) the volumes on Sānkhya and Yoga philosophies of the Encyclopaedia of Indian Philosophies series, published under the general editorship of Karl H. Potter, by M/S Motilal Banarsidass. He also served as the scholar-in-residence (sabhāpaṇḍita) of His Royal Highness, the King of Benaras, and the editor of the bi-annual multi-language journal, Purāṇam, published by the All-India Kashiraj Trust, for years, which contains innumerable research articles from his pen. Besides, he also edited four Purāṇas (Agni, Vāmana, Kūrma and Garuḍa) for the same institution.
What remains to be researched, is what it means for an enemy to be ātatāyin (lit. `with one’s bow stretched’, i.e., ready to shoot). Should the enemy be literally about to kill one? If so, there would be no time to perform a Śyena sacrifice. So, either Rāmaśaṅkara Bhaṭṭācārya thinks of preventive actions against people who are known to be about to kill someone or his is just a theoretical discussion.
In order to partly solve this problem, we checked the definition of ātatāyin in the Śabdakalpadruma (a famous Skt-Skt dictionary). This states `ready to kill’ and then quotes a verse from the commentary of Śrīdhara on the BhG discussing six types of such villains: people who are about to set something on fire, poisoners, people with a sword or a knife (śastra) in their hands, robbers, people taking away one’s wife or fields (perhaps: the products of one’s fields?). Śrīdhara then concludes: “There is no flaw in killing an ātatāyin”.
The Vācaspatyam (Skt-Skt) dictionary has a much longer entry. I am still not sure whether someone can be defined an ātatāyin for just plotting a killing —something which would allow one to prepare and perform the Śyena sacrifice.
Sudipta thinks that plotting should be included, since otherwise it might be too late to take action against the ātatāyin and the prescription about killing an ātatāyin found in Dharmaśāstra would be futile. Sudipta accordingly thinks that the Śyena is not prohibited in the case of preventing, e.g., a terrorist attack and that it is only prohibited if performed for one’s own sake, as an offensive action.
(This post has been jointly discussed by EF and Sudipta Munsi, who kindly showed me the quote mentioned above.)