May a Kohen travel from Eretz Yisrael to the diaspora?

It is forbidden for a Kohen [in Eretz Yisrael], to enter into the lands of the gentiles [in the Diaspora].[1] It is however permitted for him to do so [for the sake of a great Mitzvah[2], such as for the sake of] finding a wife, or learn Torah [if he plans to eventually return to Eretz Yisrael[3]].[4] Furthermore, some Poskim[5] rule the above prohibition only applied in previous times, when Eretz Yisrael was pure, however today, it is permitted for a Kohen to enter the Diaspora. Other Poskim[6] however argue that this law applies even today. [Practically, the custom today, is for Kohanim to travel from Eretz Yisrael to the Diaspora.[7] This custom is practiced even amongst Gedolei Yisrael who are Kohanim.[8]]

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[1] Michaber Y.D. 369/1; 372/1; Tur 369 and 372; Rif Hilchos Tuma; Rambam Avel 3; Rosh Tuma; Sheilasos Emor; Avodas Kochavim 13a; Eiruvin 47a; Mishneh Ohalos 18

The reason: As the Sages decreed impurity upon the land of the gentiles [Shabbos 15], as they bury their dead in all areas. [Shach 369/2]

[2] Beis Yosef 372 based on Tosafus Avoda Zara ibid; Perisha 372

[3] Beis Yosef 372 based on Tosafus ibid; Perisha 372

[4] Michaber 372; Avoda Zara ibid

[5] Shach 369/2; Taz 369/4; Bach 369; Perisha 369/3; Rashal on Tur 369, brought in Perisha ibid; Aruch Hashulchan 369/11

[6] Shvus Yaakov 2/98, brought in Pischeiy Teshuvah 369/5, that “The law is so clear that it is forbidden even today, that if only all the other laws would be this clear.”

[7] Maharikash; Rav Akiva Eiger 369; Chochmas Adam 159/1; Igros Kodesh 11/281

The reason: Seemingly today people are lenient because it is considered for the sake of Parnasa, or because today we are in any event considered Tmei Miesim. [Rebbe Akiva Eiger ibid]

[8] Igros Kodesh 11/281