Gittin 61A

כולי עלמא לא פליגי, כי פליגי ⁠– בלחי וקוקרי.

everyone agrees that since they are receptacles that hold the fish or animal entering them, by right the trapped animals belong to the owner of the trap. When they disagree, it is with regard to a fishhook or other traps [kokrei] that merely catch the fish or animal but are not receptacles that hold it. In such cases, there is reason to say that the owner of the trap does not take possession of the trapped animal, and therefore another person who takes it is guilty only of robbery on account of the ways of peace.

מציאת חרש, שוטה וכו׳ רבי יוסי אומר: גזל גמור: אמר רב חסדא: גזל גמור מדבריהם. למאי נפקא מינה? להוציאו בדיינין.

§ The Mishnah teaches: Taking a lost item found by a deaf-mute, an imbecile, or a minor is considered robbery on account of the ways of peace. R' Yosei says: It is full-fledged robbery. Rav Ḥisda says: R' Yosei means that it is full-fledged robbery by rabbinic law but not by Torah law. The Talmud asks: What difference is there between full-fledged robbery by rabbinic law and robbery on account of the ways of peace? The Talmud answers: If it is full-fledged robbery by rabbinic law, the victim of robbery can recover the property from the robber by appealing to judges, i.e., the court can expropriate it from him by force.

עני המנקף בראש הזית, מה שתחתיו וכו׳: תנא: אם ליקט ונתן ביד ⁠– הרי זה גזל גמור.

§ The Mishnah teaches that if a poor person gleans olives at the top of an olive tree and olives fall to the ground under the tree, then taking those olives that are beneath it is considered robbery on account of the ways of peace. According to R' Yosei, it is full-fledged robbery. A Sage taught: If the poor person gathered the olives and placed them in his hand before they fell to the ground, this is full-fledged robbery, because the poor person had already acquired legal ownership of the olives when they were in his hand.