Membership on the Universal House of Justice is confined to men.

On October 27, 1986, the UHJ stated that "it is an incontrovertible fact that all Manifestations of God known to us have been men. Moreover, it is a clear provision in Bahá’í administration that the Guardians were to be men and that membership on the Universal House of Justice is confined to men."

http://www.bahai.org/library/authoritative-texts/the-universal-house-of-justice/messages/19861027_001/19861027_001.pdf