Birkat Kohanim in entirely Israeli minyan in chutz laaretz

Question

According to the book Hilchot Tzava by Harav Zecharya Ben Shlomo a minyan of entirely Israeli soldiers in chutz laaretz should have the kohanim go up and duchan. What is the halachic rationale for that since the Ashkenazi practice in chutz laaretz is that kohanim do not ascend the duchan except for on Yom Tov?

Here in the army's actual halachic book that it itself puts out is what they say:

כא. מנהג קהילות האשכנזים בחוץ לארץ שאין נושאים כפיהם אלא במוסף של יו״ט, הנמצא בשליחות בחוץ לארץ ינהג כמנהג המקום ולא ישא כפיו )אלא אם כן מתפלל במנין ספרדי(. כהן הנמנה על משלחת קצינים העורכת תפילה לעצמה במקום שאין בו קהילה יהודית, רשאי לדעת מקצת פוסקים לשאת כפיו.

Answer 1

The minhag of those from Eretz Yisrael is to say birchath kohanim daily. While many Ashkenazim in Europe had a controversial practice of refraining from birchat kohanim during the year, this custom did not apparently exist in Israel, even among its Ashkenazim (see Pe’ath HaShulchan 2:16 and letter of SheLaH to his son in Asifath Geonim HaChadash cited here). Furthermore, the Vilna Gaon, among others, at least initially, viewed the omission as a minhag ta'uth (errant practice) in need of abolishing (see, e.g., Hilchoth HaGRA uMinhagav p. 124; Aliyoth Eliyahu, pp. 57-58, both translated here; see also Responsa Meishiv Davar 2:104; Aroch HaShulchan 128:64; and Piskei Teshuvoth II, 128:90). Since Israeli Ashkenazim apparently had the custom to say the blessings, the only reason to refrain would be to avoid conflict with a preexisting community. Where the congregation is only Israelis, there should be no such problem, and the obligation of birchath kohanim should apply.

Answer 2

Read the Hebrew quote carefully – he's talking about if a bunch of soldiers go someplace where there is no Jewish community at all.

It's not that all Diaspora Jews had the power to paint the entire map, other than Israel, as "no-birkat-Kohanim-land." Each Jewish community has its own customs, and visitors should abide by them. It happens to be that just about every Ashkenazi community outside of Israel doesn't do birkat Kohanim. If a bunch of soldiers find themselves in someplace with no Jews, then there is no local custom at all; at that point, they would fall back on their personal practice (plus the Halachic default) – which is to do it.

But if a bunch of Israelis go to ... pick someplace where there is at least one Ashkenazi synagogue and no Sephardi ones – let's say Memphis, Tennessee – then these visitors are expected to abide by the locals' communal custom, which is "no-birkat-kohanim-on-weekdays"; even if they happen to be making their own minyan today in a hotel room.

Answer 3

1. Because not saying BirKat Kohanim is a minhag Taut, people should try to duchan whether they are Israeli or not.
2. Even without #1, someone visitng another community shoud keep the "chumrot" of the place he came from and the place he's going. As a d'oraita commandement, duchaning isn't a kulla, it's a chumra, and it should be done.
3. The public nature of duchanim isn't a problem, because, again, it's a chumra, not a kulla, and violates no prohibition.