In Batzrah, Reish Lakish saw Yisraelim eating Peros without tithing them. He forbade them to do this;

He saw them drink water that Nochrim had bowed to. He forbade this.

R. Yochanan: Go retract immediately! Batzrah (is in Chutz la'Aretz, it) is not Betzer (the refuge city in Eretz Yisrael);

One cannot forbid public water.

R. Yochanan is following his opinion:

R. Yochanan: One cannot forbid public water.

Question: This implies that if the same water was privately owned, one could forbid it. Why is this? It is attached to the ground!

Answer: No, a wave detached from a body of water.

Suggestion: In any case, this is like rocks of a mountain that were uprooted;

We should be able to deduce that R. Yochanan forbids them (if they were Ne'evadim. However, he and Bnei R. Chiya argued about this, and we could not resolve who forbade and who permitted!)

Rejection: No. The case is, the Nochri took the water in his hands. This is not like rocks that were uprooted by themselves.

R. Chiya bar Aba went to Gavla and saw three things. Benos Yisrael became pregnant through Nochrim who were circumcised but did not yet immerse (to convert), Yisraelim drank wine mixed by Nochrim, and Yisraelim ate lupines cooked by Nochrim.

He did not say anything to them. He told R. Yochanan, who told him to announce that their children are Mamzerim, their wine is (forbidden like) Yayin Nesech, and their lupines are forbidden due to Bishul Akum because they are not Bnei Torah.

Their children are Mamzerim, like R. Yochanan taught elsewhere, that a convert is a Nochri until circumcision and immersion;

(R. Yochanan): If a Nochri or slave had relations with a Bas Yisrael, the child is a Mamzer.

Their wine is Yayin Nesech, due to 'Lech Lech... '

Inference: Their lupines are forbidden as Bishul Akum because they are not Bnei Torah (if we would permit them, they would treat Bishul Akum lightly), but they are permitted to Bnei Torah.

Question: Rav Shmuel bar Rav Yitzchak taught Bishul Akum does not apply to anything that can be eaten raw! (Lupines are not eaten raw. They should be forbidden to everyone.)

Answer: R. Yochanan holds like a different teaching;

(Rav Shmuel bar Rav Yitzchak): Bishul Akum does not apply to anything not proper for a king's table (lupines are not proper).

Question: May a Nochri help a Yisrael carry grapes to the Gas?

Answer (Rav Kahana): It is forbidden due to 'Lech Lech... '

Question (Rav Yemar - Beraisa): If a Nochri brought grapes to the Gas in baskets, even if the juice is flowing on the grapes, it is permitted.

Answer (Rav Kahana): I agree that b'Di'eved it is permitted. I forbid only l'Chatchilah.

A Nochri's Esrog fell into a barrel of wine; he ran and stuck his hand in to retrieve it.

Rav Ashi (to Yisraelim): Hold his hand so he cannot shake it (and forbid benefit from the wine), and tilt the barrel so the wine will flow out (into another Keli. If the Nochri would remove the Esrog, even if Yisraelim were holding his hands, we would be concerned for Nisuch.)

(Rav Ashi): If a Nochri b'Mezid was Menasech Reuven's wine, Reuven may ask him for its full (initial) value.

Question: Why is this permitted? (This is like selling Yayin Nesech to him!)

Answer: The Nochri forbade it to Reuven. It is as if he burned it. Reuven collects payment for the damage.

Support (Rav Ashi for himself - Beraisa): If a Nochri was Menasech Reuven's wine not in front of idolatry, it is forbidden;

R. Yehudah ben Bava and R. Yehudah ben Beseira permit it for two reasons:

Nisuch is done only in front of idolatry;

No one else can forbid Reuven's wine against his will. (Rashi - this shows that Reuven is entitled to collect damages from him; Tosfos - if some Tana'im permit the wine, it is unlikely that other Tana'im are so stringent to forbid taking its value from the Nochri.)