We have a merit system, which you can read about here. One of the perks of having earned many merit badges - in this specific case you need a Gold Senior Membership Merit plus four other Gold Merits - is an extra bond, no matter which community group (Ajah or Company) you belong to.
Even in the Books its only Custom not to take more than one Warder, unless your green W/ 4 or a Red W/ 0. But even Custom can be stricter than tower law at times.