From Little Froggie: “It’s been said that the Gedolim … put a cherem on the land … no Jew should ever live there again”
I believe the Tur writes the same after his father the Rosh, himself and other surviving family members left Germany, immediately after the Rindfleish Massacres of 1298 (Remember the Mordechai; Rav Mordechai Ben Hillel, famous Talmudist and Halachist was murdered during these atrocities). It’s not clear how long that Cherem was supposed to last and what geographical areas were included in that Takana.