This is a slight rewrite of a comment reply I wrote on Reddit, in a discussion about what Baha'is are to believe.
The Universal House of Justice is the undoubted authority for all Baha'is. However, the House of Justice does not provide authorized interpretation of the Writings! That is and will ever remain the sphere of the Guardianship and of Abdu'l-Baha, until the coming of the next Manifestation :
“Referring to both the Guardian and the Universal House of Justice we read these emphatic words: "The sacred and youthful Branch, the Guardian of the Cause of God, as well as the Universal House of Justice to be universally elected and established, are both under the care and protection of the Abhá Beauty, under the shelter and unerring guidance of the Exalted One (the Báb) (may my life be offered up for them both). Whatsoever they decide is of God."
From these statements it is made indubitably clear and evident that the Guardian of the Faith has been made the Interpreter of the Word and that the Universal House of Justice has been invested with the function of legislating on matters not expressly revealed in the teachings. The interpretation of the Guardian, functioning within his own sphere, is as authoritative and binding as the enactments of the International House of Justice, whose exclusive right and prerogative is to pronounce upon and deliver the final judgment on such laws and ordinances as Bahá'u'lláh has not expressly revealed. Neither can, nor will ever, infringe upon the sacred and prescribed domain of the other. Neither will seek to curtail the specific and undoubted authority with which both have been divinely invested.”
— Shoghi Effendi, World Order of Bahá’u’lláh
"The legislation enacted by the Universal House of Justice is different from interpretation. Authoritative interpretation, as uttered by 'Abdu'l-Baha and the Guardian, is a divinely guided statement of what the Word of God means. The divinely inspired legislation of the Universal House of Justice does not attempt to say what the revealed Word means -- it states what must be done in cases where the revealed Text or its authoritative interpretation is not explicit. It is, therefore, on quite a different level from the Sacred Text, and the Universal House of Justice is empowered to abrogate or amend its own legislation whenever it judges the conditions make this desirable."
— Letter from the Universal House of Justice to an individual believer titled "Teaching versus Proselytizing", January 03 1982
This teaching of the distinction of the spheres of authority of the House of Justice and the Guardianship is not a mere technicality. It is at the very core of the Baha'i Covenant and foundations for our beliefs as Baha'is. It is an extraordinary novel advance of differentiation and maturity in religious governance with deep implications in the very meaning of how we are to understand this Revelation.
