[nicholassmith]

I don't think so, or at least non-trivially anyway. Same reason jammers are prohibited as they have a potential spillover, as you can't definitively say 'this is the range it'll work in'.

On the part of service providers also monitoring it it's difficult, a fair few prisons are actually within reasonably populated areas so it'd have to be pretty accurate signal tracking so you didn't get some spillover.