Answer to The Riddle

PARSHAS HASHAVUA  נשא                          
                                           RIDDLE

It's Tuesday morning (no קריאת התורה) The Rav tells you not to Daven
in this Shul. (There is no טומאת מת)
For your friend, the Rav says that he can Daven in that Shul.
When asked why the Rav answered because you are a כהן and he is a לוי.
A few minutes later the Rav allowed a different כהן to Daven in that Shul.
When asked why his answer was because he is from out of town.

                                                  ANSWER

According to Harav Hagaon Reb  S.Z. Auerbach zt”l,
Ashkenazi כהנים in Chutz La’aretz should לכתחילה
not Daven in a Sephardic Minyan (Shachris) so not to
get into a situation of having to  Duchen. (Days when
Minhag Ashkenaz is not to Duchen)

R. Shlomo Zalmen also holds that an Israeli כהן who

happens to be in Chu”l may Daven and Duchan

לכתחילה in a Sephardic Minyan.

Hence the first כהן was told not to Daven in the
Sephardic Shul. Whereas the second כהן was from
E Yisrael, he may Daven & Duchan in a Sephardic Shul.
 

The ערוך השלחן, writes, "Not having ברכת כהנים (in Chutz L'aretz ) every day has no legitimate reason. It is a bad Minhag. However, we can't do anything about it. It is as if a בת קול FROM HEAVEN APPEARED telling us not to do it. There were 2 Gedolim from the previous generation who attempted to change it. They both failed and said that it must be מן השמים not to change the Minhag."