Q: Should litigation involving commercial transactions be ruled in accordance with classic Halachah?

A: Although Torah law is eternal, where the common commercial practice (minhag hamedinah) differs from classic Halachah, beis din should rule according to the common practice, since commercial transactions are made with this understanding. This does not violate the prohibition against adjudication by civil law, since the parties did not accept its authority but rather mutually committed themselves to gain or be liable according to the common practice (Pischei Teshuvah, C.M. 3:2; Responsa Maharshach 2:229).

Moreover, some write that for transactions that are valid only on account of situmta (business practice), such as lottery rulings, beis din might even recommend adjudicating before a panel of professionals well acquainted with the business practice, since the halachah here is to rule in accordance with what is fair and just according to the practiced business procedures (Chelkas Yoav, vol. II, addendum, p. 176).