That is a strange thing. There is an Emerald Society of the Chicago Police Department:

http://www.copsinkilts.com/

...if you explore the website, you'll find a roster of the band. Bear in mind that in these parts everybody has some kind of Irish connection but I don't know if they make it a prerequisite that you have Irish ties for membership...

The Chicago Fire Department has its own pipe band though I can't find a direct web link to a page about them.

One can only assume that the Emerald Societies began as rather, you should excuse the expression, clannish groups but one would think that there would be no need for that these days and that they'd be a little more all inclusive.

Best

AA

"I'd never want to belong to a club that would have me as a member." - Groucho Marx