UHJ has no right at all to change any law that Bahá’u’lláh has specifically revealed.

Although the Universal House of Justice has to apply and supplement the laws of the Aqdas it has no right at all to change any law that Bahá’u’lláh has specifically revealed. As clearly stated by the Guardian, the provisions of the Kitáb-i-Aqdas “remain inviolate” during the entire Dispensation.

(From a letter dated 28 April 1974 written by the Universal House of Justice to an individual believer)

https://www.bahai.org/library/authoritative-texts/compilations/universal-house-of-justice-compilation/5#692131014