Well, that sure will teach those criminals! Or maybe it will teach those criminals, hmm... no guns on city property, hmm... easy pickin’s, hmm...
If he figures out how to tax the monetary “exchange” he may save his city from immediate bankrupcy. He may even be able to encourage the “exchanges” to boost city revenue. Looks like he has identified a way to encourage this exchange. Next he needs to figure out how to tax it.