(Gemara): The Chatzer of a Nochri is like a Dir or Sahar of animals.

Question (Rabanan, to R. Eliezer ben Yakov): If Yisrael and an animal lived in a Chatzer, does the [pen for] animal not forbid?! Just like the [abode of] animal forbids, a Nochri forbids.

Question (R. Eliezer ben Yakov, to Rabanan): If Yisrael and an animal lived in a Chatzer, does the animal forbid?! (Surely, a Hefker animal does not forbid. It forbids only due to its owner.) Just like an animal does not forbid, a Nochri does not forbid. (We explained this like HA'GAON RAV C. KANIEVSKY, SHLITA.)

(R. Yakov bar Acha citing R. Yosa citing R. Yochanan): The Halachah follows R. Yochanan ben Nuri [who says that Hefker items acquire Shevisah].

Question (R. Hoshayah): Why did he need to teach this? (The general rule is, the Halachah follows the lenient opinion in Eruv!)

Answer: [It is needed in a case when Rabanan are stringent and an individual is lenient], like R. Eliezer ben Yakov (a Tosefta teaches that the Halachah follows him). However, [one might have thought that the Halachah is] like Rabanan who argue with R. Yochanan ben Nuri. (We explained this like PNEI MOSHE.)