The Kitáb-i-Aqdas
Notes
49.The Lord hath ordained that in every city a House of Justice be established   ¶30
The institution of the House of Justice consists of elected councils which operate at the local, national and international levels of society. Bahá’u’lláh ordains both the Universal House of Justice and the Local Houses of Justice in the Kitáb-i-Aqdas. ‘Abdu’l-Bahá, in His Will and Testament1, provides for the Secondary (National or Regional) Houses of Justice and outlines the method to be pursued for the election of the Universal House of Justice.
In the verse cited above, the reference is to the Local House of Justice, an institution which is to be elected in a locality whenever there are nine or more resident adult Bahá’ís. For this purpose, the definition of adult was temporarily fixed at the age of 21 years by the Guardian, who indicated it was open to change by the Universal House of Justice in the future.
Local and Secondary Houses of Justice are, for the present, known as Local Spiritual Assemblies and National Spiritual Assemblies. Shoghi Effendi has indicated that this is a “temporary appellation” which,
…as the position and aims of the Bahá’í Faith are better understood and more fully recognized, will gradually be superseded by the permanent and more appropriate designation of House of Justice. Not only will the present-day Spiritual Assemblies be styled differently in future, but they will be enabled also to add to their present functions those powers, duties, and prerogatives necessitated by the recognition of the Faith of Bahá’u’lláh, not merely as one of the recognized religious systems of the world, but as the State Religion of an independent and Sovereign Power.2
 
1 Will and Testament of ‘Abdu’l-Bahá, p. 14
2 Shoghi Effendi, The World Order of Bahá’u’lláh, p. 6