Justice Stephen Breyer provided the swing vote in each 5-4 case, one of which upheld a display of the Ten Commandments and another that struck it down. The rulings were issued on the same day in June 2005.
The difference between the two cases was based in the context of each display. One, in Texas, involved a Ten Commandments monument displayed among other religious and secular symbols. The other monument, in Kentucky, stood alone.
In the Texas case, the display, one of many on the lawn of the Texas State Capitol, had been there since 1961. It was considered by the court to have historic significance, and therefore was not found to be in violation of the Establishment Clause.
In the Kentucky case, the court held that the display of the Ten Commandments in the courthouse in the absence of other messages or historic symbols did violate the Establishment Clause.
In the Slidell case, the ACLU argues that the Jesus painting is much like the Kentucky display and is an obvious endorsement by the government of religion.
"There's not an appearance of government neutrality toward religion in this case," said Katie Schwartzmann, a staff attorney for the ACLU Foundation of Louisiana.
Two outside legal experts who spoke to ABC News were split on Slidell. David Hudson, with the Freedom Forum's First Amendment Center, said he thinks the painting would be illegal because it's not surrounded by other displays presenting various messages.
"It seems like the ACLU might have a stronger argument here under existing precedent," Hudson told ABC News. "The kicker would be [that] the composition of the U.S. Supreme Court has changed since [the Kentucky decision] came down."
Since the Texas and Kentucky decisions were issued, Roberts and another conservative justice Samuel Alito have joined the court after Chief Justice Rehnquist's death and the retirement of Justice Sandra Day O'Connor.
Douglas Laycock, a professor of constitutional law at the University of Michigan's law school, consulted Slidell's Lamz before the judge made the decision not to remove the controversial display. Laycock told ABC News he advised Lamz that he has a chance to uphold the Slidell display.
Interestingly, there are cases in which the ADF and the ACLU come down on the same side of First Amendment cases, although both organizations say they have never directly worked together.
In a New Jersey case decided in December, the ACLU supported the ADF's clients, who argued their daughter's First Amendment rights were violated when her elementary school prohibited her from singing a religious song in a school-sponsored talent show. A federal judge sided with the ADF and the ACLU.
The two organizations also support California high school student Tyler Chase Harper's right to wear a shirt opposing homosexuality in protest of his school's day dedicated to gay rights. The ADF is representing Harper in the case, and David Blair-Loy, an attorney in the ACLU's San Diego office, said the ACLU plans to file a brief supporting the ADF's argument.
"Civil liberties can make strange bedfellows at times," Blair-Loy said. "Our position will align with ADF's position in terms of freedom of speech."
While the New Jersey and California cases both involve federally funded schools, the ACLU contends it's the students, not the schools, who are exercising their First Amendment rights. The ACLU says no reasonable person would interpret their expressions as the desires of the schools themselves to promote one religion over others. Therefore, the schools are not violating the Establishment Clause.
Back in Slidell, it appears that Lamz has no plans to follow in the footsteps of former Alabama Chief Justice Roy Moore, who was removed from office after he refused a federal court order to take down his Ten Commandments monument. Lamz has said that if a federal judge orders the painting out, he'll comply.