In 2011, a shipment of somewhere between 200 to 300 small clay tablets on their way to Oklahoma City from Israel was seized by U.S. Customs agents in Memphis. The tablets were inscribed in cuneiform—the script of ancient Assyria and Babylonia, present-day Iraq—and were thousands of years old. Their destination was the compound of the Hobby Lobby corporation, which became famous last year for winning a landmark Supreme Court case on religious freedom and government mandates. A senior law enforcement source with extensive knowledge of antiquities smuggling confirmed that these ancient artifacts had been purchased and were being imported by the deeply-religious owners of the crafting giant, the Green family of Oklahoma City. For the last four years, law enforcement sources tell The Daily Beast, the Greens have been under federal investigation for the illicit importation of cultural heritage from Iraq.

These tablets, like the other 40,000 or so ancient artifacts owned by the Green family, were destined for the Museum of the Bible, the giant new museum funded by the Greens, slated to open in Washington, D.C., in 2017. Both the seizure of the cuneiform tablets and the subsequent federal investigation were confirmed to us by Cary Summers, the president of the Museum of the Bible.

From its founding in 1970, the Greens’ Hobby Lobby chain has been more than simply a suite of craft stores. The Greens have used it as a model of a business run on Christian values. Stores are closed on Sundays in order to give employees time to attend church. The company employs four chaplains, and offered a free health clinic to staff at its headquarters long before free health care came into political vogue. The Greens have also used the Hobby Lobby platform to spread their Christian message far and wide: The company annually places full-page ads celebrating—in their words— “the real meaning of Christmas, Easter, and Independence Day” in newspapers across the country.

But the Greens went from evangelical players to bona fide Christian celebrities in June of 2014 when they won a Supreme Court case, Burwell v. Hobby Lobby. It granted them exemption from the Obamacare mandate to provide certain forms of contraception to their employees; forcing the company to do so, the Supreme Court ruled, would have violated the Greens’ deeply-held Christian beliefs.

If the investigation ends with a decision to prosecute, on either criminal or civil charges, the Greens may be forced to forfeit the tablets to the government. There may also be a fine involved. The Green family, who successfully forced the federal government to legally recognize their personal moral standards, now find themselves on the other side of the docket, under suspicion of having attempted to contravene U.S. laws.

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When Summers spoke with us, he made it sound as if the ongoing federal investigation was simply the result of a logistical problem. “There was a shipment and it had improper paperwork—incomplete paperwork that was attached to it.” That innocuous phrase—“incomplete paperwork”—makes it sound as if some forms were simply missing a date or a signature. That is rarely the case with questionably-acquired ancient artifacts—and were the problem merely logistical, the chances are slim that it would take four years to resolve.

Summers suggested that the tablets were merely “held up in customs,” as if this was merely a case of bureaucratic delays. “Sometimes this stuff just sits, and nobody does anything with it.” But an individual close to the investigation told us that investigators have accumulated hundreds of hours of interviews, which doesn’t sound like bureaucratic delay—and which also suggests that there is more at stake here than merely a logistical oversight.

An attorney familiar with customs investigations explained that they often center on improperly filled out paperwork. There are two types of customs declarations: informal entry and formal entry. Informal entry is generally for shipments that have a collective monetary value of under $2,500; formal entry is for anything above that. In cases where people are trying to bring something into the country that they shouldn’t, one of the common ways to do so is to undervalue whatever the item is, often by misidentifying it, so that it goes through the expedited informal-entry process rather than the more closely scrutinized formal entry.

If someone looking to bring antiquities into the U.S. knows that the artifacts should never have left their country of origin, or lack proper provenance, the only way to get them through customs is to lie: about the country of origin, about the country of export, about the value, about the identity. (This happened recently in the case of a Picasso worth $15 million, which was listed on the customs declaration as a “handicraft” worth $37.) One source familiar with the Hobby Lobby investigation told us that this is precisely what happened in this case: The tablets were described on their FedEx shipping label as samples of “hand-crafted clay tiles.” This description may have been technically accurate, but the monetary value assigned to them—around $300, we’re told—vastly underestimates their true worth, and, just as important, obscures their identification as the cultural heritage of Iraq.

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Steve Green, the CEO of Hobby Lobby, admitted that among his family’s extensive collection they might have some illegally-acquired antiquities, though he denied having ever knowingly done anything wrong. “Is it possible that we have some illicit [artifacts]? That’s possible,” he told us for a story slated to appear in a forthcoming issue of The Atlantic. It seems unlikely that this case, however, is one of simply misunderstanding the relevant laws. The paperwork misidentifying the antiquities as “tile samples” certainly suggests otherwise. What’s more, however, in the summer of 2010, Patty Gerstenblith, a law professor at DePaul University working in the area of cultural heritage, met privately with the Greens in order to explain to them precisely these issues: how to do due diligence with regard to provenance and how to watch out for legal complications with regard to antiquities sales. It cannot be said that the Greens were totally ignorant of the world in which they were engaging. And a year later, the Greens imported the tablets that have now become the subject of the federal investigation.

The Greens are worth $4.5 billion or so. If they are indeed prosecuted, no fine could make a significant dent in their financial well-being. But for a company and a family that have built their reputation on a particular set of Christian values, this investigation may hurt more than any financial penalty could.

—with additional reporting by Michael Daly