The separation of church and state includes the freedom to require employees to follow Church teachings, said a legal group responding to a lawsuit over the firing of an employee of the Kansas City – St. Joseph diocese after her same-sex "marriage" became public.

"If dioceses are forced to employ people who do not follow Church doctrine, the government will have corrupted the Church, which will no longer be able to minister freely in accordance with its faith," Erik Stanley, Alliance Defending Freedom senior counsel, said Sept. 18.

Stanley said that a church "is not obligated to employ those who willingly act contrary to the church's teaching," noting that this right was upheld by the Supreme Court in a unanimous decision two years ago.

Alliance Defending Freedom has filed a brief in support of the Diocese of Kansas City-St. Joseph, asking for the dismissal of a lawsuit filed on behalf of Colleen Simon, a fired church employee.

Simon began working as director of social ministries for the diocese's St. Francis Xavier parish in July 2013. She said that her civil marriage, to a woman who is a pastor at a local Lutheran church, was known to the parish at the time it hired her under its previous pastor.

In May, the church's new pastor asked for Simon's resignation after a newspaper article identified her as married to a woman. She did not submit a resignation letter but continued to work, and was fired a few days later.

In a June letter, the diocese's human resources director said in a letter to Simon that her conduct "contradicts church laws, discipline, and teaching and the diocesan policy on ethics and integrity in ministry."

Simon's lawsuit seeks unpaid wages, fringe benefits, compensation for emotional distress, punitive damages and attorney fees. The lawsuit is being handled by the Circuit Court of Jackson County, Missouri.

At a July news conference, Simon said her firing was "unjust" and said she wanted to return to her position.

Alliance Defending Freedom's brief said the lawsuit itself was unjust and endangered religious freedom.

"It is for a church alone to decide who is and who is not qualified to receive church authority and communicate religious doctrine," the brief said.

"The relationship between a church and its ministers reaches to the core of internal church governance: an area into which courts may not intrude. Courts rightly look with suspicion upon the employment lawsuits of former church ministers because such cases are fraught with constitutional hazards."

The brief said that Simon was a "ministerial employee" and an "at-will employee who could be terminated at any time and for any reason."

Kevin Theriot said that the courts "have rightly and regularly upheld the freedom of churches to make employment decisions according to the very faith that the church espouses."

"To do otherwise would be to undermine the church itself and invite the government into the very realm that the First Amendment says the government cannot tread. This lawsuit is baseless and should be dismissed."

In July, the Diocese of Kansas City-St. Joseph's communications director Jack Smith said the diocese regretted that the situation has resulted in litigation, saying "it is our sincere hope that the matter can be resolved amicably."

"In general, as a Church we have the right to live and operate according to our faith and Church teachings," he said.

"As needed, we will defend our constitutional freedom to practice our faith and uphold the integrity of our mission and public witness."