Council prerogative allows the 10 district Council members to control city land within their districts. If the city wants to sell a property, it needs a Council ordinance, which by tradition — not law — must be sponsored by the district's Council member. The seven at-large members usually go along because they need district Council members' votes for their own initiatives. There are no real rules guiding prerogative and some Council members have used that power to obstruct city projects and, in a few instances, to use it for leverage.