Archbishop Salvatore Cordileone has called passage of a gay marriage law in Illinois a “serious injustice.”

Illinois Governor Pat Quinn, a Democrat, signed the legislation during a ceremony held last week in downtown Chicago. The law takes effect on June 1.

Cordileone, who leads the United States Conference of Catholic Bishops' (USCCB) Subcommittee for the Promotion and Defense of Marriage and heads the diocese of San Francisco, criticized passage of the law in a blog post.

“The decision by the Illinois legislature and the governor to redefine marriage in law does not alter the natural reality that marriage is and can only be the union of one man and one woman,” Cordileone wrote. “Furthermore, marriage redefinition is a serious injustice. The law exists to safeguard the common good and protect authentic rights, especially the right of children to have a married mother and father.”

During the debate in the House, Speaker Mike Madigan referred to Pope Francis' response to gay clergy: “Who am I to judge?”

Without mentioning Madigan by name, Cordileone, a vocal opponent of allowing gay couples to marry, said that it was dishonest to use the pope's words to support marriage equality.

“When referring to the family, Pope Francis said very clearly in his first papal encyclical: 'I think first and foremost of the stable union of man and woman in marriage.' And very recently, the Pope offered these words: 'Let us therefore propose to all people, with respect and courage, the beauty of marriage and the family illuminated by the Gospel!' Pope Francis has forcefully reminded us that we are to show love and respect to all people and to seek their greatest good, and he therefore continues to clearly promote and defend marriage and family, recognizing that this is in everyone's best interest as members of a common society. In fact, when confronting an effort to redefine marriage in his home country of Argentina, he said as Archbishop of Buenos Aires: 'The identity of the family, and its survival, are in jeopardy here: father, mother, and children.' He even added: 'At stake is the total rejection of God's law engraved in our hearts.' It is therefore disgraceful that some legislators would manipulate the words of Pope Francis to suggest that he would support marriage redefinition.”