That does not seem to be strictly foreclosed by the rules ( http://networkchallenge.darpa.mil/rules.aspx http://networkchallenge.darpa.mil/rules.aspx ), but the

That does not seem to be strictly foreclosed by the rules ( http://networkchallenge.darpa.mil/rules.aspx http://networkchallenge.darpa.mil/rules.aspx ), but there is this nice catch all clause which I suspect would come into play ("DARPA reserves the right to disqualify a participant whose actions are deemed to violate the spirit of the competition for any reason, including but not limited to, the violation of laws or regulations in the course of participation."). I do note that "[b]alloons will be in readily accessible locations, visible from nearby roadways and accompanied by DARPA representatives." I suppose you'd want to make sure to hard check the balloons and verify the representative part.