Tosefta for Avodah Zarah 108:13

But orlah and diverse crops (kilayim) of the vineyard (see Orl. 3:7) are [treated] the same for Gentiles in the Land of Israel, in Syria, and outside the Land (cf. Avodah Zarah 54b:6). But Rabbi Yehudah says, the [laws of] the fourth-year vineyard do not [apply to] a Gentile in Syria. And the Sages say, they do apply (Ter. 3:9). Said Rabbi Yehudah, it so happened with S'gabion (שְׂגַבְיוֹן not שביון) the head of the synagogue of Achziv, that he had purchased from a Gentile a fourth[-year vineyard] in Syria and had paid [the Gentile] money for it. And he came and asked Rabban Gamaliel, who had been passing from place to place [about whether such a vineyard is liable]. And [Rabbi Gamaliel] said to him, "Wait until [this situation] becomes [the subject of] halachah" (i.e., Rabban Gamaliel did not know the answer). They [the Sages] said to him [Rabbi Yehudah], "This is no proof [that such a vineyard is not liable]. Not only that, but [Rabban Gamaliel later] sent him [S'gabion] in the hand of a deaf-mute messenger (alt., "a secret message," see Lieberman), [stating,] 'What you did, you did, but do not teach [others] to do so.'"