He said that under Canon law the Christian faithful had "the right and even at times the duty to manifest to the sacred pastors their opinion on matters which pertain to the good of the Church".
Mr Butler said they are also "protesting at the disproportionate sanction of dismissal handed down by the Congregation for the Doctrine of Faith (CDF) to American priest Fr Roy Bourgeois for his support of women priests, despite his "39 faithful years in the priesthood".
On Nov 19, the Maryknoll congregation issued a statement announcing that the US priest had been dismissed from the priesthood by the CDF for his involvement in the ordination of Janice Sevre-Duszynskaa in 2008 in Kentucky.
WACI has accused the CDF of an "unacceptable infringement of Christian thought" over its "suppression of any discussion within the Church of the issue of women’s ordination". It has also accused the Maryknoll Order of betraying Fr Bourgeois, claiming the order did not defend the priest in the face of the Vatican’s pressure.
Mr Butler said WACI had priests and religious members who support the aims of the group in relation to women priests, but would not be naming them "for fear that they too will incur dismissal or silencing".
He also explained that under canon law Fr Bourgeois and the Irish priests had no right of appeal, and said this was something WACI intended to raise in its letter.