Correct shirt for semi-formal (aka, back tie)?

[kilted redleg]

Can't speak for your side of the yard Jock but, US Customs is known to seize whatever they can. A few years back when citie rules on ivory were in effect; unless a piper had paperwork to show their pipes were made prior to date specified in the law ivory mounted pipes were being seized at a regular rate. There was a story carried in the local news media about a young piper who had his great great grandfather's [who came to the US in 1800's] ivory pipes seized at customs for lack of paperwork. Happily after a call from their US senator who knew the family the pipes were returned.