It might make sense to consider the laws here to be more like general guidelines. Certainly in the bureaucracy, two different clerks on two different days will likely as not tell you something totally the opposite with that unbending porteno conviction.Blend in and do as you see the locals doing and you will probably be fine, unless you have an unlucky moment, in which case the actual law might not make so much difference. In my personal experience the police here are friendly, helpful, and not heavy handed control freaks.
However I too would be interested to know the actual laws on this. Anybody know?