Psychological and educational issues need to be addressed in such a case by those who are familiar with the its dynamics. We will concentrate on the halachic issues.
Simply moving someone’s possessions around while searching is not stealing, which is defined as taking something away from its owner, even temporarily,[1] or actually using it physically without permission.[2] However, going through another’s belongings compromises his right to privacy, a right that halacha defends. The gemara[3] discusses in detail the concept of avoiding hezek re’iya (damage caused by being able to see sensitive matters). Rabbeinu Gershom instituted a cherem[4] against reading someone’s letters without permission. According to many poskim, the prohibition against doing so existed previously; the ban just added additional sanctions.[5]
May one invade a thief’s privacy in order to catch him? As a rule, one may take the law into his own hands to legitimately protect his interests. One who recognizes his stolen object on the thief’s property may enter the property and take it forcibly if opposed.[6] (According to one opinion, he should not do so surreptitiously and thereby look like a thief himself.) Presumably, this allows suspending some of the thief’s civil rights, including his privacy. The Chikekei Lev[7] leaves unresolved the question whether beit din may allow one who suspects that a letter contains improperly damaging information about him to read it in order to know how to proceed. The prominent dayan, Rav Shlomo Daichovsky,[8] discusses the issue of listening devices. He says that the Chikekei Lev would agree that an individual who has strong reason to expect that someone is harming him may use such a device to protect his interests. All the more so, he continues, it is permissible if one has the opportunity to prevent another from sinning. In our case, it is a sin to steal or to possess stolen goods, and the staff might have been able to facilitate the youngster’s receiving counseling, which he likely needs.
One obvious problem is that barring definite knowledge of the suspect’s guilt, one could be acting improperly toward an innocent person. However, there is precedent in this regard, as well. The gemara[9] tells of how Mar Zutra suspected someone of stealing a silver goblet because he showed disregard for someone else’s property. Mar Zutra physically pressured the suspect until he confessed to the crime. The Panim Meirot[10] cites more recent rulings on the issue of taking physical steps based on strong suspicions.
Another issue is that, classically, it is the one with the personal stake who may take steps to protect himself, whereas others should not.[11] However, this is apparently to prevent people who should not be involved from ‘sticking their noses in’ without judicial authority. In our case, though, it would be improper to allow the alleged victim to act based on his suspicions alone.[12] The camp’s responsible staff members, who are mandated to supervise the campers’ welfare and conduct, are the proper people to be involved.
Thus, if the staff’s upper echelons, in consultation with its rabbis, were convinced that the suspicions justified a search, they could have halachically done so. (It would be prudent, though, that one consult appropriate counsel regarding the legality of his actions and consider all relevant consequences.)