Catholic Church Conservation: Roman veto

From NCR Online:

In general, church-watchers say that policy is intended to defend the theology of apostolic succession, in which decision-making power in the church is believed to flow through the sacrament of holy orders. Although religious brothers take vows and are generally seen as equals within their communities, under the church's canon law they are considered laity.

I can understand why apostolic succession is important for the exercise of authority within the local Church and the universal Church -- but why is it necessary for religious orders or other associations that are a part of a Church?