DURHAM, N.C. - The Supreme Court's decision in a constitutional dispute over a cross on federal park land in California should clarify a handful of questions regarding the Establishment Clause, says a Duke University law professor.

The Establishment Clause of the First Amendment has generally been interpreted to prohibit the preference of one religion over another, among other things.

At issue is the display of a cross in the Mojave National Preserve. The court heard arguments in the case on Wednesday.

The American Civil Liberties Union, representing a former National Park Service employee, sued to have the cross removed or covered after the agency refused to allow the placement of a Buddhist memorial nearby.

The Obama administration supports Congress' decision to transfer the site to private ownership, arguing that such a measure should remedy any constitutional questions.

"The court essentially has two questions to answer," says Joseph Blocher, a Duke law professor whose principal academic interests include constitutional law and the First and Second Amendments.

"The first is whether the challenger has standing to file the case at all. The second is whether Congress can avoid the Establishment Clause problem by simply transferring to a private party the small piece of land on which the cross stands, while allowing the cross to stay right where it is and even retaining some property rights in it."

Blocher says standing doctrine basically requires a person to have a concrete and particularized injury before they can go to court. But this doesn't mean they have to be physically hurt -- taking offense can be enough.

"What makes this case interesting is that the challenger is arguing not that the sight of the cross is offensive in and of itself, but the sight of the cross demonstrates an offensive preference for one religion over others," Blocher says.

Blocher says the case is not about whether the Establishment Clause prohibits all religious symbols on public land, noting that the Supreme Court has said repeatedly that it doesn't, at least where those symbols are placed in a context that makes it clear the government isn't favoring one religion over another.

But the lower courts have already held that this particular cross does violate the Establishment Clause.

"So the question now is, what can the government do to cure the Establishment Clause violation? One of the hard questions here is whether we care about what a reasonable observer of the cross would think," Blocher says. "Since the cross is surrounded by public land and set back pretty far from the road, it might still look like an endorsement of a particular religious symbol even though the government has mostly given up title to the small plot of land where the cross stands."