OkCupid did not respond to my request for comment.

To understand the law professors’s complaints, it helps to briefly review the law that governs research funded by the federal government—the so-called “Common Rule.”

With some exceptions, the Common Rule requires all federally funded research to adhere to two procedures.

The first requirement: All human subjects must give informed consent before the experiment begins. That means more than saying “yes”: Human subjects must be given enough information by researchers to know what they’re getting themselves into.

The second: Any research involving humans must be vetted by an “institutional review board,” or an IRB, which vets the legality of the experiment.

This two-edged regime applies to all research that the U.S. government funds. Maryland's law, House Bill 917, extends those protections to all research conducted in the state, even if it isn’t federally funded. According to Grimmelmann and Henry, that catches Facebook and OkCupid, who both admitted to doing research on such large sets of users that they almost certainly included Maryland residents.

But was what Facebook and OkCupid did research? The two law professors argue that yes, it was.

“Both Maryland law and federal law define research as a systematic investigation designed to develop or contribute to generalizable knowledge,” says Henry. Because Facebook published the results of its study in the a scientific journal, the Proceedings of the National Academy of Sciences, and because OkCupid shared the results of its study online, the two companies clearly intended for their findings to be taken generally.

Since publishing his blog post, OkCupid’s CEO, Christian Rudder, has gone on a national press tour to promote his new book about the riches of user data. Rudder claims that his experiments on the dating site can help people understand all sorts of issues, down to the most pressing: OkCupid studies, he lightly writes, prove that racism “is pervasive.”

Grimmelmann and Henry wrote to Facebook and OK Cupid, informing them of the alleged law-breaking. OkCupid did not respond, but Facebook lawyer Edward Palmieri did. In a letter excerpted in the Washington Post, Palmieri said: “The federal Common Rule and the Maryland law you cite were not designed to address research conducted under these circumstances and none of the authorities you cite indicates otherwise.”

Facebook insists that the testing it was doing originated as product testing. And, indeed, “consumer acceptance study” is a specifically exempt kind of research under both federal and Maryland law.

But, in an email, Henry writes:

The Facebook deception study is categorically different from corporate optimization. It was not about product testing or maximizing business-oriented results for Facebook. It involved deceptively manipulating people's emotions for the purpose of testing a scientific hypothesis about emotional contagion, the results of which were ultimately published in a peer-reviewed scientific journal.

Grimmelmann said that this difference—between corporate testing and academic research—has been debated before.