The Universal House of Justice is infallible.

The Universal House of Justice is infallible. In the Tablet of Carmel Baha’u’llah refers to the Ark which will sail upon Mount Carmel. Shoghi Effendi states, ‘Baha’u’llah refers to an Universal House of Justice “Ark”, whose dwellers are the men of the Supreme House of Justice. The “sailing of the Ark” of His laws is a reference to the establishment of the Universal House of Justice, ...” In His Will and Testament ‘Abdu’l-Baha states that the Universal House of Justice, with the Guardian, is ‘under the care and protection of the Abha Beauty, under the shelter and unerring guidance of His Holiness, the Exalted One ... Whatsoever they decide is of God. Whoso obeyeth him not, neither obeyeth them, hath not obeyed God; whoso rebelleth against him and against them hath rebelled against God; whoso opposeth him hath opposed God; ...

(A Basic Baha'i Dictionary by Wendi Momen)