The Talmud discusses whether orlah applies outside the Land of Israel, and derives from the phrase 'when you come into the land' that orlah is fundamentally a land-based commandment. The Gemara ultimately rules that orlah in the diaspora is a halakha le-Moshe mi-Sinai — an oral law tradition from Sinai — and is therefore still prohibited, but with a more lenient standard.
תְּנַן הָתָם: הֶחָדָשׁ אָסוּר מִן הַתּוֹרָה בְּכׇל מָקוֹם, עׇרְלָה הֲלָכָה, וְהַכִּלְאַיִם מִדִּבְרֵי סוֹפְרִים. מַאי הֲלָכָה? אָמַר רַב יְהוּדָה אָמַר שְׁמוּאֵל: הִלְכְתָא מְדִינָה. עוּלָּא אָמַר רַבִּי יוֹחָנָן: הֲלָכָה לְמֹשֶׁה מִסִּינַי. שַׁלְחַהּ רַב יְהוּדָה לְקַמֵּיהּ דְּרַבִּי יוֹחָנָן. שְׁלַח לֵיהּ: סְתוֹם סְפֵיקָהּ, וְאַבֵּד וַדָּאַהּ, וְהַכְרֵז עַל פֵּירוֹתֵיהֶן שֶׁטְּעוּנִים גְּנִיזָה. וְכׇל הָאוֹמֵר אֵין עׇרְלָה בְּחוּצָה לָאָרֶץ – לֹא יְהֵא לוֹ נִין וָנֶכֶד, ״מַשְׁלִיךְ חֶבֶל בְּגוֹרָל בִּקְהַל ה׳״. אָמַר רַבִּי אַסִּי אָמַר רַבִּי יוֹחָנָן: עׇרְלָה בְּחוּצָה לָאָרֶץ הֲלָכָה לְמֹשֶׁה מִסִּינַי. אֲמַר לֵיהּ רַבִּי זֵירָא לְרַבִּי אַסִּי: וְהָתַנְיָא: סְפֵק עׇרְלָה בָּאָרֶץ – אָסוּר, בְּסוּרְיָא – מוּתָּר, בְּחוּצָה לָאָרֶץ – יוֹרֵד וְלוֹקֵט! ״אֶשְׁתּוֹמַם כְּשָׁעָה חֲדָה״ אֲמַר לֵיהּ: אֵימָא כָּךְ נֶאֶמְרָה: סְפֵיקָהּ מוּתָּר, וַדָּאָהּ אָסוּר.
We learned in a mishna there (Orla 3:9): The new crop is forbidden by Torah law everywhere; orla is forbidden outside of Eretz Yisrael according to a halakha, as the Gemara will immediately explain; and diverse kinds are forbidden outside the land by rabbinic law. The Gemara asks: What is this halakha, mentioned with regard to orla? Rav Yehuda says that Shmuel says: It is the local halakha, i.e., this was the practice of Jews in places where they settled. Ulla says that Rabbi Yoḥanan says: It is a halakha transmitted to Moses from Sinai. Rav Yehuda sent a question to Rabbi Yoḥanan concerning the halakha with regard to orla outside of Eretz Yisrael. Rabbi Yoḥanan sent him the following response: Conceal, i.e., do not publicize, the halakha that produce whose orla status is uncertain is permitted; and destroy, i.e., prohibit entirely, produce whose orla status is certain; and with regard to the produce of those who are lenient in this halakha, declare that it requires interment, as it is prohibited to derive benefit from such produce. And whoever says that there is no prohibition of orla outside of Eretz Yisrael will have neither a child nor a grandchild “who shall cast the line by lot in the congregation of the Lord” (Micah 2:5). Rabbi Asi says that Rabbi Yoḥanan says: Orla is forbidden outside of Eretz Yisrael by a halakha transmitted to Moses from Sinai. Rabbi Zeira said to Rabbi Asi: But isn’t it taught in a baraita: With regard to produce whose status concerning orla is uncertain, in Eretz Yisrael it is forbidden, in Syria it is permitted, and outside of Eretz Yisrael one goes down and gathers it? And if orla is forbidden outside of Eretz Yisrael by a halakha transmitted to Moses from Sinai, why is produce whose status concerning orla is uncertain permitted in Syria? Rabbi Zeira “was dismayed for a while” (Daniel 4:16), and then Rabbi Asi said to him: Say that it is stated like this, i.e., explain that the halakha transmitted to Moses from Sinai was that outside of Eretz Yisrael produce whose status concerning orla is uncertain is permitted, and produce whose status concerning orla is certain is forbidden.