Dear Rabbi Kornfeld,
You wrote in the Insights-
>>(b) However, RASHI (as cited by the TOSFOS HA'ROSH and the TUR (see also
SHILTEI GIBORIM)) says that the Gemara is indeed referring to a situation
where someone owes the Talmid Chacham money. The Gemara means that a
Talmid Chacham may not only take back the money that is owed to him (like
every other person may also do, even someone who is not a Talmid
Chacham), but he may even enforce his right to the money by putting the
other person in Niduy until he gets back the money. (A layperson, though,
does not have this authority.) This is also the explanation of the
CHIDUSHEI HA'RAN<<
According to this why was Resh Lakish criticized for putting someone into Niduy who stole from him?
Gershon
TOSFOS there (17a, DH Niduy) cites in the name of RABEINU TAM that the accepted practice of that place (where Reish Lakish was guarding a field) was that the people would take fruit from the trees and then pay the owner later. As such, the person whom Reish Lakish put into Niduy was not stealing at all; it was Reish Lakish's error, and that is why he was criticized. The RITVA, citing the RA'AVAD, answers similarly, but he adds that that year, the owner of the field had decided not to sell the fruit, and thus the person who took the fruit was indeed acting wrongly even though he intended to pay the owner later. That is why Reish Lakish put him into Niduy. Still, though, it was improper to put him into Niduy, since he should have first warned the person and informed him that the owner had changed his practice. Had Reish Lakish informed him, the person might have stopped taking the fruit.
Kol tuv,
Mordecai