Earlier quoted context omitted.
They hire someone to take each batch from them. So at best, you can only ever prosecute a fall guy, not the skilled counterfeiter. In essence, it's easier to make any counterfeiting illegal, and then not prosecute the person who once prints a picture of a stamp and tapes it to a letter. Trying to make counterfeiting legal in certain situations can be abusable.
And so they get prosecuted for incitement, conspiracy and organized crime. Seriously, as a rule of thumb, none of those extremely simple loopholes you can come up in five seconds of thinking work: there people were before you, and they too could think (even though in case of lawmakers it can sometimes be hard to imagine that they can actually think).
And yeah, these loopholes don't work because people tried them and now counterfeiting one stamp is illegal. That's my point.