עלה תחומין - Techum on Yom Tov

Based on The Practical Halachos of Techum Shabbos by Rabbi Yonason Posnik shlita

Techum Shabbos applies equally to Shabbos and Yom Toν (Shulchan Aruch, Orach Chaim 397:3). Even though in many circumstances one may carry on Yom Tov, one must still be careful not to walk outside of the Techum. The same applies to Yom Kippur. One may wonder why in fact one is not allowed to walk outside the Techum at all on Yom Tov. After all, one may carry on Yom Tov, even in a place with no Eruv, for food preparation purposes – ochel nefesh, so why is Techum different? Shouldn't it be permitted for food preparation purposes?

The answer is that only melachah is permitted for food preparation needs. Techum, however, is not one of the 39 melachos, but rather a separate halachah. As such, it does not fall into the Torah's dispensation of ochel nefesh (Chasam Sofer OC 149).