But before the majority of the Assembly comes to a decision, it is not only the right but the sacred obligation of every member to express freely and openly his views, without being afraid of displeasing or alienating any of his fellow-members. In view of this important administrative principle of frank and open consultation, the Guardian would advise you to give up the method of asking other members to voice your opinion and suggestions. This indirect way of expressing your views to the Assembly not only creates an atmosphere of secrecy which is most alien to the spirit of the Cause, but would also lead to many misunderstandings and complications. The Assembly members must have the courage of their conviction, but must also express whole-hearted and unqualified obedience to the well-considering judgement and directions of the majority of their fellow-members.
(Shoghi Effendi, Lights of Guidance, p. 177)
While it is not forbidden for Bahá’ís to consult with a Local Spiritual Assembly other than their own, it is highly discouraged, because it could potentially undermine the authority and prestige of the Assembly under whose jurisdiction one resides.
(Universal House of Justice, NSA USA - Developing Distinctive Bahá’í Communities)