After more than a half century, Santa Monica Nativity display at Palisades Park is no more

"When you have a right to free speech and the government tells you that you can only do your speaking in private, that violates the Constitution. That's not a rationale for violating the First Amendment," Becker said of Santa Monica restricting the Nativity display to church lawns.

Constitutional scholars agree that legal precedents over the past half-century have found religion has a right to free expression on public property.

"Although government may not promote a religious message, the court has ruled that private religious expression in a public forum doesn’t violate the Establishment clause as long as other expression is allowed on equal terms," wrote Charles Haynes, senior scholar at the Freedom Forum First Amendment Center, in the Washington Post.

Rassbach said that local governments can be more creative in defining those equal terms than what Santa Monica decided to do. He said that governmental bodies from Congress to town councils have marked certain days and times for celebrations of all kinds, and Christmas can fall under those guidelines.

"There is no requirement under the establishment or free speech clauses (of the First Amendment) to give opponents of those celebrations the same voice at the same time as the celebrators themselves," he said.

In other words, each group can have its own day and time in the park, rather than all at once.

One issue Gaylor and religious liberty advocates do agree on is that the law in the area of Christmas displays is murky. Rather than clear guidelines, the courts have provided nuanced rulings. The most notable has been mockingly referred to as the "reindeer rule," in which the 1984 Supreme Court determined that mixing enough secular decorations in with religious can neutralize the message when government gets involved.

Becker acknowledged before Thursday's anticipated dismissal that appealing to the 9th Circuit Court of Appeals, which he said is not always friendly to religion, risks coming away with another precedent that could hurt religious expression.

"We’ve got a mountain to climb here, and I have a good client who is interested in protecting and preserving First Amendment rights of everyone," Becker said. "If the judiciary don’t support us, at the very least we can say we did our best to try to overcome a wall atheists have erected between us."