If you can't get quickly to an agreement about such a thing, or if the members of the team that didn't get their way actively rebel (or worse sabotage), you are working with a team of divas.
(note: of course developers whinge, as long as you stick with the team decisions once their are made, whinge all you want)
Or you're working on such a trivial problem that it should have been given to an individual, not a team.
A well working team will probably do as you say - volunteer an individual to write the rule in an email and follow it from there on.
If you going to introduce changes in a team, like for example introducing Agile (the proper way) or you are starting a new project, you want to quickly gauge the team dynamic, and that's a good exercise.
It kinda reminds me of that buzzfeed article "53 Signs Your Boyfriend Is Really Three Children In A Trenchcoat".
(make sure to hit F5 a few times)