John Greim via Getty Images You have to be religious if you want to give an opening invocation in the Pennsylvania state House, say the chamber's leaders.

Over the past few years, leaders in the Pennsylvania state House have repeatedly maintained that only religious individuals are fit to deliver the opening invocation before each session. Now, they may end up having to defend that position in court.

A group of atheist and secular organizations filed a federal lawsuit on Thursday, claiming that Republican leadership is unconstitutionally discriminating against nonbelievers who wish to offer guidance to lawmakers in accordance with their sincerely held beliefs.

The controversy dates back to August 2014, when two members of local atheist groups each submitted a request to deliver an opening invocations at a daily session of the Pennsylvania House. A month later, then-House Speaker Samuel H. Smith (R) shot down the applications on the grounds that the body was not “required to allow non-adherents or nonbelievers the opportunity to serve as chaplains.” A similar request months later was met with an official rule change stating that guest speakers “shall be a member of a regularly established church or religious organization or shall be a member of the House of Representatives.”

This is a violation of precedent established in the Supreme Court’s 2014 ruling in Greece v. Galloway, the plaintiffs contend. That decision upheld the constitutionality of government prayer, as long as it maintains a policy of nondiscrimination. Atheist and secular groups interpret this ruling as prohibiting preferential treatment of religion over nonreligion, which is also a pillar of the First Amendment’s Establishment Clause.

“The court emphasized that the town of Greece expressly allowed atheists to give opening invocations, and that was an important factor in the court’s ruling upholding the town’s practice,” said Alex Luchenitser, associate legal director at Americans United for Separation of Church and State, a Washington, D.C.-based advocacy group representing the plaintiffs.

Republican leaders in Pennsylvania and elsewhere disagree, and have routinely claimed that the Supreme Court ruling doesn’t explicitly call for the inclusion of nonbelievers. A spokesman for Pennsylvania House Speaker Mike Turzai (R), who, along with other House members, is named as a defendant in the suit, said in a statement: “We believe our rule and policy comports with the Constitution and is consistent with long history of legislative prayer as recognized by the various Supreme Court cases.”

Similar disputes have fueled contentious battles over the role of religion in state and local chambers around the nation. At issue is a broader question of whether nonbelievers must be allowed to participate in proceedings that have traditionally been seen as forums for religious expression.

Months ago in Arizona, for example, an atheist lawmaker spoke out after years of being barred from leading an invocation over concerns that he wouldn’t mention God. When he was finally given an opportunity to deliver these opening remarks, the House majority leader declared it illegitimate because they hadn’t referenced a higher power.

These arguments have increasingly become fodder for lawsuits. The Freedom From Religion Foundation, a nonprofit that advocates for the separation of church and state, sued the U.S. House chaplain and other lawmakers earlier this year, claiming they’d unconstitutionally discriminated against the group’s co-president by blocking him from leading a secular invocation before Congress.

Despite the ongoing quarrels, many governmental bodies have taken steps toward fuller acceptance, whether due to genuine interest in inclusivity or fear of legal ramifications. An atheist invocation in Waterloo, Iowa, went over with little fanfare earlier this year, which could speak to the argument of many nonbelievers: They want to be included in these ceremonies for the purposes of unity, not to divide or denigrate religion.

Satanists have even seen victories in the campaign for inclusion, and have recently delivered invocations in Pensacola, Florida, and Soldotna, Alaska.

Nonbelievers in Pennsylvania say theirs is the latest fight for full equality and acceptance of all Americans.

“To say that theists can do this but nontheists cannot is quite clearly discrimination, but it also sends a message to the nontheist community that our voice doesn’t matter, that our point of view doesn’t matter,” Brian Fields, president of Pennsylvania Nonbelievers and a plaintiff in the case, told The Huffington Post. “It reinforces religious ideas that nontheists don’t have a say when it comes to morality.”

“For us, this is an opportunity to present another point of view, to say, ‘Hey, look, we’re in this together.’” Brian Fields, Pennsylvania Nonbelievers president

Sessions of the Pennsylvania House have been opening with prayer for more than three centuries, according to PennLive, and a look at the recent history of the practice suggests the legislature hasn’t done much to foster diversity.

In the period from Jan. 8, 2008, through Feb. 9, 2016, the plaintiffs found records of 575 invocations, 265 of which were delivered by guests. Of these, they documented 23 instances of Jewish rabbis giving prayers, three invocations given in the Muslim tradition and just one where the religious affiliation of the guest was not stated. All of the invocations over this period were monotheistic in nature.

“There’s a lot of talk about Jesus in the invocations, there’s a lot of talk about God and God’s role in the individual lives of the people presenting,” Fields said.

But nobody has spoken on behalf of the growing ranks of religious “nones,” including atheists, agnostics and others who do not identify with any formal religion. These people now make up nearly one-quarter of the U.S. population, and among them are more than 2.5 million nonreligious Pennsylvanians, according to American Atheists, an advocacy group that has joined the lawsuit.

“For us, this is an opportunity to present another point of view, to say, ‘Hey, look, we’re in this together,’” Fields said. “It wouldn’t be my intention to bring up God, but to bring up morality and justice and fairness and those ideas that we hold to be important, rather than a strictly religious invocation.”

And none of that should be threatening or offensive to lawmakers who considering themselves religious, Luchenitser says.

“These are unifying, uplifting invocations that don’t criticize or disparage religion,” he said. “Our plaintiffs want to present a positive, inclusive message that includes everyone and doesn’t denigrate anyone.”

Below is a draft copy of the invocation Fields had planned on giving, which was included in the lawsuit:

Thank you for inviting me to speak today. Our commonwealth was founded on the principles of tolerance, respect, and equality. As we gather, let us fully consider each citizen of this commonwealth as equals in the eyes of the law. May reason and rationality guide our decisions, and may those decisions be considered to be in the best interests of all of us. We are a commonwealth of many different people working together. We are a commonwealth of Muslims, Jews, Hindus, Sikhs, Buddhists, Christians, agnostics, atheists and many, many others. We may disagree in many respects, but we can all agree here that our laws are the foundation of our civil society. To that end, I ask that those gathered here today remember that the reason that society works is the fair and judicious application of those laws discussed here. To close, I would like to offer the words of Albert Einstein: “Nothing truly valuable can be achieved except by the unselfish cooperation of many individuals.” Thank you.

This story has been updated to include comment from Turzai.