Rev. Thomas Tobin, Bishop of the Roman Catholic Diocese of Providence, has barred gay Catholics from entering a civil union.

Governor Lincoln Chafee on Saturday signed a civil unions bill into law, making Rhode Island the fifth after Illinois, New Jersey, Delaware and Hawaii to recognize gay and lesbian couples with civil unions. Chafee, who supports giving gay couples the right to marry, expressed reservations about the law but added that it would protect thousands of families, saying that the legislation “brings tangible rights and benefits to thousands of Rhode Islanders” and that it “provides a foundation from which we will continue to fight for full marriage equality.”

Even before Chafee signed the bill into law, Tobin released a statement criticizing it.

“I am deeply disappointed that Rhode Island will establish civil unions in our state,” he wrote at The Rhode Island Catholic. “The concept of civil unions is a social experiment that promotes an immoral lifestyle, is a mockery of the institution of marriage as designed by God, undermines the well-being of our family and poses a threat to religious liberty.”

Lawmakers shifted from supporting a gay marriage law to civil unions after it became clear a marriage bill wouldn't clear the Republican-controlled Senate.

Gay rights groups objected to an amendment sponsored by Rep. Arthur J. Corvese that exempts religious organizations from the requirement that they treat gay couples in a civil union as they would any other married couple.

Tobin, however, suggested he doesn't support any government recognition of gay couples, and barred gay Catholics from entering a civil union.

“[T]he Church reminds its members that homosexual activity is contrary to the natural law and the will of God and, therefore, is objectively sinful. Persons with same-sex attraction are required to live the Christian virtues of chastity and modesty, as all persons are.”

“Because civil unions promote an unacceptable lifestyle, undermine the faith of the Church on holy matrimony, and cause scandal and confusion, Catholics may not participate in civil unions. To do so is a very grave violation of the moral law and, thus, seriously sinful. A civil union can never be accepted as a legitimate alternative to matrimony.”