They are voting on a measure, such a proposed bill. While we don't know what the exact measure is, there are clues as to what the vote is about. The measure they are voting on would loosen alcohol restrictions in some way. They do not actually explain why the son would have easier access to alcohol, but that is a clue as to the contents. The "extra tax revenue" which "comes at a cost" also implies that more alcohol will be sold under this measure, causing the state to collect more in alcohol taxes due to the reduced restrictions on alcohol.