It's forbidden to leave the Land of Israel ever, except to learn Torah, or to get married, or to escape from enemies or to do business.
To leave Eretz Yisrael to settle permanently in the Diaspora is forbidden - unless there's a serious famine in the land.
Whoever lives in Eretz Yisrael - his sins are forgiven. Even walking 4 cubits in Eretz Yisrael is a Mitzva.
Applies to everybody, everywhere, always.
Verse: "You shall not go back on that way again" (Devarim 17:16)
Source: The Chafetz-Chaim's Sefer haMitzvot haKatzar; Prohibition 192
Monday, 6 Kislev 5771