Eighteenth century writer and philosopher the Marquis de Sade spent the last 13 years of his life in prison for his crimes of writing pornographic novels such as Justine and Juliette.

Today those who explore and write about similar sexual fantasies online—now known as BDSM and grounded in the consent of all participants—are suffering similar acts of censorship as the eponymous literary sadist who preceded them by two centuries. The biggest difference is that the church and state have been supplanted as chief censors by private companies such as payment service providers Visa, Mastercard, and PayPal.

Five years ago EFF defended the right of publishers such as Smashwords to publish written descriptions of transgressive sexual conduct, against PayPal's threat to cancel payment services unless they withdrew such works from sale. (Following our campaign, in which we were joined by more than two dozen other free speech groups, PayPal relented.) In the same year the Nifty Archives Alliance, which publishes erotic stories, had its donation page temporarily suspended by its payment processor for fear of violating Visa and Mastercard rules. Two years ago, Backpage.com had its payment services suspended by Visa and Mastercard for providing a platform to advertise sexual services.

This year it's the turn of adult social network FetLife, which just lost its ability to process credit card payments because it offers a platform for members to discuss and to post depictions of consensual BDSM practices. In this instance the ban appears to have come down from one of the credit card networks, which shut down both of the merchant accounts that FetLife used to process payments, justifying this to one merchant with complaints about "blood, needles, and vampirism" on the website, and to the other with the vague explanation of "illegal or immoral reasons".

If any illegal content were on the website that would indeed be cause for concern, but there is no evidence of this. The last time FetLife lost payment processing services in 2013, it was on the basis of complaints of illegal child pornography on the site. Yet on closer investigation, this turned out to amount to sexualized cartoon drawings of the Simpsons, which even if they may have been in poor taste, were constitutionally protected speech under U.S. law. Even so, the site clamped down on fantasy depictions or descriptions of underage sex and incest going forward, and its payment processing services were restored.

There is no further evidence of illegal content on FetLife today than there was back then. Nor does it seem obvious the card networks' content rules have been infringed; both networks prohibit imagery of "non-consensual sexual behavior" and "non-consensual mutilation of a person or body part", but consensual BDSM is neither of these. Nonetheless, the credit card ban has had its desired effect of further constricting the range of permissible speech on FetLife, with the site introducing new restrictions on a broad range of edgy sexual practices, including consensual non-consent, race play, drug and alcohol use, and scarification.

Despite all this, their payment services still haven't been reinstated, and it's unclear how they can be. In the meantime FetLife does still accept payments via Bitcoin, which due to its open and decentralized infrastructure, is much more resistant to censorship pressures. While there may one day be a future in which digital currencies like Bitcoin are so widely adopted that it's easy for many websites to thrive on them alone, today we live in a world where credit card oligopolies can effectively shut down digital speech they find annoying or offensive.

In the course of a round of buck-passing between PayPal and the credit card networks during the Smashwords dispute, Visa had written "Visa would take no action regarding lawful material that seeks to explore erotica in a fictional or educational manner. As you note in your letter, Visa is not in the business of censoring cultural product." While we don't know which of the card networks were responsible for the latest FetLife ban, such fine sentiments seem hard to square with it.

It's also difficult to discern what's behind this latest crackdown, but the least likely scenario is that it was a case of proactive self-policing by the credit card network. More likely, this is a case of Shadow Regulation in which the hand of government, or some third party acting as self-appointed morals campaigner, has reached a secret agreement with the payment network behind the scenes. In this context, it may be worth noting that Attorney-General Jeff Sessions recently indicated that he would consider reviving the Justice Department's Obscenity Prosecution Task Force.

Whatever the source of the pressure to which the payment network acceded, EFF remains deeply concerned that payment companies aren't doing enough to consistently push back against demands to privately censor lawful sexual content online. In an age where the 50 Shades movies are playing in mainstream cinemas across the country, society ought to have moved on from the days when pornographers such as de Sade were jailed and his books burned. The best way for payment companies to discern when online content has crossed the line into obscenity is to rely on courts to make that judgment.