Arkansas, which is poised to erect a new Ten Commandments monument on the grounds of its state capitol, has just rejected a request by a Hindu group to erect a statue of the god Hanuman there. Constitutionally, the rejection is permissible: The US Supreme Court permits the government to pick and choose what symbols it wants to project in public space. But turning down a statue of the Hindu deity with the jaw of a monkey also calls into question the constitutionality of the Ten Commandments statue—because the government can’t endorse one religion at the expense of others.

Confused? I hope so. If you aren’t, you get an A in constitutional law—but something’s gone wrong with your logic function. The Supreme Court’s twin doctrines on government speech and endorsement of religion are in tension with each other, as the Arkansas situation shows.

Let me take a moment to explain the law as it stands. In an important 2009 case called Pleasant Grove v. Summum, the Supreme Court said that statues in public parks count as “government speech."

When it speaks, the government is generally free to endorse or reject any viewpoint it wants. This is very different from when the government restricts private speech—then it’s prohibited by the First Amendment from favoring one viewpoint over others. Thus it matters hugely whether a particular act of expression is called government speech, where almost any rule goes, or private speech, where almost all limitations are barred.

This doctrine is the reason Arkansas can say no to the Hindu group: because the state is speaking when it chooses monuments for the state capitol. In the Summum case, too, the local government refused to erect a religious monument proposed by members of the Summum religion. It’s also why the court this past June said that Texas could refuse to put a Confederate battle flag on its license plates.

The catch is that, even when the government is speaking, there’s at least one constitutional limit on what it can say: It can’t endorse religion. The reason is the establishment clause of the Constitution as interpreted by the Supreme Court. Arkansas can’t put up a statue saying, “Christianity is the right religion and Hinduism isn’t."

“But wait," you say, pulling out your Bible. Isn’t that exactly what the Ten Commandments mean when God tells the Israelites “You shall have no other gods before me"? Doesn’t a stone monument of the Ten Commandments communicate precisely that Judaism or Christianity is true and that other polytheistic faiths—like Hinduism—are false?

Here’s where things really get messy. In a pair of cases decided the same day in 2005, the Supreme Court upheld the constitutionality of a Ten Commandments monument on the grounds of the Texas state capitol and struck down two displays inside courthouses in Kentucky that also featured the Decalogue. The swing vote in both cases was Justice Stephen Breyer, who in a cryptic opinion seemed to say that the Texas monument was old and big and the Kentucky displays were new and easily removable.

Arkansas legislators are probably hoping that their new Ten Commandments monument will be upheld because Texas’s old one was. Their lawyers will argue in court that the monument doesn’t endorse religion, just acknowledges the place of Judeo-Christian tradition in Arkansas and US history. Or they might say that most Arkansans consider the Ten Commandments central to their lives.

Rejecting the Hanuman statue makes their case harder. It’s pretty clear that the Arkansas Legislature wants to endorse Christianity and doesn’t want to endorse Hinduism.

Conversely, if the Hanuman statue had been accepted, the courts would have been more likely to uphold the Ten Commandments monument. Then it would appear that Arkansas was aiming to allow a diverse range of cultural and religious traditions to be represented on the state capitol’s grounds.

The upshot is that, if religious people want to express their values symbolically under the current legal regime, they probably need to embrace religious diversity. If they don’t like that option, they can choose to keep their religion private.

This isn’t far from James Madison’s original view of religious liberty in America. He argued that with so many sects (albeit 99% Christian) there was little worry about establishing a national religion, because the public wouldn’t be able to agree on one.

There are hard cases when it comes to government speech and religion. Old established traditions really are hard to uproot. Christmas Day and Thanksgiving, which both imply God, couldn’t be disestablished without offending most Americans. “In God We Trust" is newer, but also couldn’t be abolished as the national motto without incurring anger and backlash.

But a new Ten Commandments monument in Arkansas isn’t needed to maintain social peace and religious inclusiveness. If the Arkansans want to become multiculturalists and embrace Jesus and Hanuman, fine. If not, leave the statehouse grounds as they are now.

Some scholars also think the state can’t openly speak in a way that discriminates on the basis of race— like erecting a purely symbolic sign saying “This town prefers white people." But the court has never actually said so.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.BLOOMBERG.