Some countries use prison labor legitimately such as using products from the prison system's work programs and vocational education. Or to produce item's that the prison system needs to sustain itself (the Florida prison system uses inmate industries to produce the inmates' uniforms and an inmate farm system to supplement their diet)
Other countries view their prisons as free slave labor to be exploited.
I suspect the regulations prohibitting their carriage is so that GB doesn't inadvertantly participate in the latter. That said, it makes it illegal for us here to send you most surplus military uniforms as the issue uniforms are produced by Federal Prison Industries (as were the older military furniture items)
Not to be confused with authorized optional uniform items that are considerred upgrades and are authorized for military members' private purchace.
Really good point - one I never considered. Too many meetings at work today or perhaps I'd have thought of it.