At Triad games last year I met a gentleman who makes haggis commercially. He informed me that for some weird and unfathomable reason, the FDA will not allow the use of a sheep's stomach! He uses large size bologna casing which is allowed. He claimed to use all of the other traditional ingredients though.

I find it strange in that here in E. Carolina, there is a thing called a "Tom Thumb" sausage that is essentially the haggis recipe but using pork instead. It is made in a pig's stomach. That is apparently ok with the FDA. (strange folk, govt. bureaucrats.)