How odd. The ASA is a UK body, and therefore not of interest to most of us. Plus it only deals in advertising, not including company-run websites or in-store (or in-pub, presumably) advertising. I don't think I've ever seen an actual ad for Árainn Mhór in any medium dealt with by the ASA.
Did the nice lady mention where the alleged offending statement was printed?
The ASAI, Ireland's equivalent body, doesn't deal with text on packaging, company websites or point-of-sale material.
I doubt any complaint to either body about Árainn Mhór being brewed abroad would be upheld since, as far as I'm aware, Árainn Mhór has no paid ads anywhere.