Who ruled Bree?

Since Bree had a ditch, hedge, gates, gatehouses, and gatekeepers, all of which would have required communal labor and/or money to maintain, there must have been some organized leadership, if only of the "village elders" sort.

In the prologue to FOTR the obligations of the Shire Hobbits to the old kings basically consisted of "speeding the King's messengers", which might be taken to mean keeping roads and bridges in repair. Probably some sort of communal labor was called for here as well, as with the Shire Postal system, and the "Bounders".