Establishment and Functions:
Regarding the establishment of “National Assemblies,” it is of vital importance that in every country, where the conditions are favorable and the number of the friends has grown and reached a considerable size, such as America, Great Britain and Germany, that a “National Spiritual Assembly” be immediately established, representative of the friends throughout that country.
Its immediate purpose is to stimulate, unify and coordinate by frequent personal consultations, the manifold activities of the friends as well as the local Assemblies; and by keeping in close and constant touch with the Holy Land, initiate measures, and direct in general the affairs of the Cause in that country.
It serves also another purpose, no less essential than the first, as in the course of time it shall evolve into the National House of Justice (referred to in Abdu’l-Baha’s Will as the “secondary House of Justice”), which according to the explicit text of the Testament will have, in conjunction with the other National Assemblies throughout the Baha’i world, to elect directly the members of the International House of Justice, that Supreme Council that will guide, organize and unify the affairs of the Movement throughout the world.
It is expressly recorded in Abdu’l-Baha’s Writings that these National Assemblies must be indirectly elected by the friends; that is, the friends in every country must elect a certain number of delegates, who in their turn will elect from among all the friends in that country the members of the National Spiritual Assembly.
(Shoghi Effendi: Baha’i Administration, pp. 39-40)

In countries where the local Baha’i communities had sufficiently advanced in number and in influence measures were taken for the initiation of National Assemblies, the pivots round which all national undertakings must revolve. Designated by Abdu’l-Baha in His Will as the “Secondary Houses of Justice,” they constitute the electoral bodies in the formation of the International House of Justice, and are empowered to direct, unify, coordinate and stimulate the activities of individuals as well as local Assemblies within their jurisdiction. Resting on the broad base of organized local communities, themselves pillars sustaining the institution which must be regarded as the apex of the Baha’i Administrative Order, these Assemblies are elected, according to the principle of proportional representation, by delegates representative of Baha’i local communities assembled at Convention during the period of the Ridvan Festival; are possessed of the necessary authority to enable them to insure the harmonious and efficient development of Baha’i activity within their respective spheres; are freed from all direct responsibility for their policies and decisions to their electorates; are charged with the sacred duty of consulting the views, of inviting the recommendations and of securing the confidence and cooperation of the delegates and of acquainting them with their plans, problems and actions; and are supported by the resources of national funds to which all ranks of the faithful are urged to contribute.
(Shoghi Effendi: God Passes By, pp. 332-333)

…it is one of the vital functions of the National Spiritual Assembly to be always in touch with local conditions in every community and to endeavour, through personal contacts and by means of regular correspondence, to guide the friends, individually and collectively, in all their activities.
(Shoghi Effendi: National Spiritual Assembly, p. 110)

The Guardian welcomes the step taken by your Assembly to increasingly devote its meetings to the consideration of major policies and plans, and to dwell less on matters of detail and of mere secondary administrative character. He would, however, urge that all decisions, unless of a trivial and insignificant nature dealing purely with routine work, should be reached after careful and conscientious deliberation by all the nine members. Any tendencies towards decentralization, or the delegation of authority to any person or body to make decisions on matters which directly and solely concern the National Spiritual Assembly itself, would be harmful and should be checked at the very outset. It is for this very reason, namely to enable the National Spiritual Assembly to properly and fully discharge its functions of consultation and deliberation on issues that concern the national community under its jurisdiction, that its membership has been limited to nine, so that it may not be too unwieldy for making decisions that would often require quick action and mature deliberation by all the members. In order to safeguard the distinctive character of such a central and authoritative institution more frequent gatherings would seem imperative, particularly as the problems which it will be called upon to deal with are destined to increase in number and importance with the steady expansion of the Faith in North America.
(Shoghi Effendi: National Spiritual Assembly, pp. 120-121)

In the Baha’i Faith there are matters of principle affecting the operation of Baha’i institutions, which are outlined in the writings of the Faith as well as in the Constitutions of National and Local Spiritual Assemblies. Obviously, National Assemblies will face situations and problems which have to be resolved but are not fully covered by these texts. In such matters the National Assembly should adopt its own procedures suited to the conditions and requirements of its own national community. It may be found useful to adopt a procedure followed by another National Spiritual Assembly; certainly there is no objection to such a course of action, provided it is clear that in the final analysis such issues are left to the discretion of the National Assembly itself.
In matters of principle, therefore, there should be uniformity, while in matters of detail and procedure not only is diversity permitted, it is also encouraged. As conditions vary from country to country and, indeed, can vary from community to community within the country, Shoghi Effendi repeatedly advised the friends that they should be uncompromising in principle but flexible in subsidiary details.
(The Universal House of Justice: Lights of Guidance, p. 38)

We should respect the National Spiritual Assembly and the Local Spiritual Assembly because they are institutions founded by Baha’u’llah. It has nothing to do with personality, but is far above it.
(Shoghi Effendi: National Spiritual Assembly, p. 96)

…the Guardian wishes me to again affirm his view that the authority of the National Spiritual Assembly is undivided and unchallengeable in all matters pertaining to the administration of the Faith … and that, therefore, the obedience of individual Baha’is, delegates, groups, and assemblies to that authority is imperative, and should be whole-hearted and unqualified. He is convinced that the unreserved acceptance and complete application of this vital provision of the Administration is essential to the maintenance of the highest degree of unity among the believers, and is indispensable to the effective working of the administrative machinery of the Faith in every country.
(Shoghi Effendi: Lights of Guidance, p. 36)

What the Guardian is aiming at is to remind the friends, more fully than before, of the two cardinal principles of Baha’i Administration, namely, the supreme and unchallengeable authority of the National Spiritual Assembly in national affairs and working within the limits imposed by the Declaration of Trust and By-Laws, and the untrammelled freedom of the Convention delegates to advise, deliberate on the actions, and appoint the successors of their National Assembly.
(Shoghi Effendi: National Spiritual Assembly, p. 102)

Anything whatsoever affecting the interests of the Cause and in which the National Assembly as a body is involved should, if regarded as unsatisfactory by Local Assemblies and individual believers, be immediately referred to the National Assembly itself. Neither the general body of the believers, nor any Local Assembly, nor even the delegates to the annual Convention, should be regarded as having any authority to entertain appeals against the decision of the National Assembly. Should the matter be referred to the Guardian it will be his duty to consider it with the utmost care and to decide whether the issues involved justify him to consider it in person, or to leave it entirely to the discretion of the National Assembly.
(Shoghi Effendi: Directives of the Guardian, p. 50)

This is indeed a clear indication of the Master’s express desire that nothing whatever should be given to the public by any individual among the friends, unless fully considered and approved by the Spiritual Assembly in his locality; and if this (as is undoubtedly the case) is a matter that pertains to the general interest of the Cause in that land, then it is incumbent upon the Spiritual Assembly to submit it to the consideration and approval of the national body representing all the various local assemblies. Not only with regard to publication, but all matters without any exception whatsoever, regarding the interests of the Cause in that locality, individually or collectively, should be referred exclusively to the Spiritual Assembly in that locality, which shall decide upon it, unless it be a matter of national interest, in which case it shall be referred to the national body. With this national body also will rest the decision whether a given question is of local or national interest. (By national affairs is not meant matters that are political in their character, for the friends of God the world over are strictly forbidden to meddle with political affairs in any way whatever, but rather things that affect the spiritual activities of the body of the friends in that land).
(Shoghi Effendi: Unfolding Destiny, p. 8.)