Chicago Cardinal Francis George does not believe gay marriage is possible because it violates the laws of nature.

Illinois lawmakers, who legalized civil unions for gay couples 2 years ago, are expected to take up the issue when they reconvene for a lame-duck session. Each chamber will meet for 3 days, with the Senate's meeting starting on Wednesday, January 2. State Senator Heather Steans and state Rep. Greg Harris, Democrats from Chicago, have said they will only press ahead with a vote if they believe the marriage bill will clear the current General Assembly. New members will be sworn in on January 9.

George, the head of the Catholic Conference of Illinois and the Archbishop of Chicago, called on Roman Catholics to oppose passage of the legislation in a letter sent to priests, the Chicago Tribune reported.

“Civil laws that establish 'same sex marriage' create a legal fiction,” George wrote. “The State has no power to create something that nature itself tells us is impossible.”

George added that parishioners should not alienate gay family members over the issue.

“Good pastoral practice encourages families to accept all their children and not break relationships with them,” he said.

Priests may opt out of publishing the letter in their parish bulletins.

George apologized last January for comments he made comparing gay rights activists to the Ku Klux Klan.