As simple and as faceless as a lethal injection.

Every day there is a new report about how Facebook, Google, Twitter, Snapchat, Instagram and other giants of social media censor content, banish certain commentators for incorrect views, and otherwise work in a steady if unsystematic way to homogenize political opinion within an acceptably progressive bandwidth. Ideas are scoured for “racism”—as contentiously defined by the intellectual stylebook of the hard left Southern Poverty Law Center, which the media have set up as an “authority” on hate speech; freedom of speech is seen a nuisance rather than a guarantee of personal liberty and true diversity of opinion.

But there is an even more sinister threat to the first amendment than the social media, a threat that operates in a stealth way in the most crucial arena of our economic system. It is corporate giants Master Card and Visa, which now use their unparalleled financial power to determine what speech should be allowed and what speech should be silenced.

Most Americans use a credit or debit card everyday and take these two corporations as much for granted as the light switch or the automobile ignition. We buy things with their cards ranging from the annual vacations to the daily groceries. These two interlocked corporations are the drum majors marching us into a cashless society. They are powers unto themselves, but their eminence rests on our money and the fees they exact to accommodate our transactions.

The cards they issue are even more critical to the vendors whom they pay. Without the ability to accept charges to these cards as payment many businesses would in effect be out of business.

Unlike the comparatively clumsy and very public efforts of the social media to erase “offensive”—all too often a synonym for conservative—opinion, the cognate machinations of Visa/Mastercard take place more remotely and without response in the dark space of the mundane financial transaction.

It is as simple and as faceless as a lethal injection: An individual who wants to support an organization online makes the digital donation and is then informed that Visa/Mastercard will not process it. Neither the individual nor the organization he wishes to support are told that it is on a blacklist, let alone informed how or got there or how to get off. The donor is denied his right to put his money where his mouth is. The organization he supports is condemned to death by strangulation in the dark in a world designed by Kafka.

The Freedom Center had such an experience a few months ago when online donations were overnight peremptorily refused by Visa/Mastercard with no reason given and no protest accepted. We were able to create enough noise about this injustice—in the media and with the threat of legislative attention—that the credit card giants turned the power back on just as capriciously as they had turned it off.

We were lucky. Robert Spencer, whose jihadwatch.org is one of the indispensable sites for understanding the intentions and the threat of Islamic terrorism, has been shut down from receiving supporters’ donations for several weeks now, and is forced to try to keep jihadwatch going on a shoestring while Visa/Mastercard imperiously ignores demand letters and threats of court action from his attorneys. The anti Semitic Nation of Islam’s credit card donations are processed; the anti Islamist jihadwatch’s are not.

This oligopoly acts with the faceless finality of an IRS lien when it sets itself up as lawmaker, judge and jury with the power to decide which speech should be allowed and which should be shut down. It kills free speech not by arguing against the ideas it disapproves of, but by the silence of the arbitrary act, using the financial system to accomplish the deed.

An analogue to what Visa/Mastercard has done and is doing was once banned by the 1964 Civil Rights Act which, among other things, gave U.S. citizens, specifically African Americans, the right to sit at a lunch counter and have a sandwich the way any other America could. This opening of public accommodations to African Americans in effect told private businesses that they were accommodations open to the public and that all people, regardless of race, comprised that public and that they could not deny the civil rights of anyone seeking to use their facility.

Can there be any doubt that MasterCard and the other major card companies are similarly a public accommodation? Over half the people of the United States who own a debit or credit card use as their sole method for paying bills. (Most of the other half uses them too, just not as frequently.) In 2015 there were 69.5 billion debit card payments with a value of $2.56 trillion and 33.8 billion credit card payments with a value of $3.16 trillion–together adding up to around 6 trillion in an economy of 19 trillion.

This is a very sizable public accommodation. More importantly it is immense power, power that can be and is being used to shut down the civil rights of people who want to support the speech of the Freedom Center, Jihadwatch, other conservative groups and anyone else in our political universe.

Visa/Mastercard tell the people whose rights they strangle that they can always get funds to the organizations whose speech they want heard by other means. That is true—people can write a check and mail it or make a cash withdrawal from their bank and drive it to the offices of the organization they support just as black people in the South in the 1950s could have eaten at some other lunch counter in a more remote part of town.

The money these corporate giants hold belongs to private individuals who have a fundamental civil right to direct that money—which they pay the oligopoly a handsome fee to distribute to organizations they approve of and for the opinions they want heard in the public square. Their money is their speech. When they hit the “donate” button on a nonprofit’s website they are saying, “I believe….”as surely as if they were holding a placard in a march or writing to a legislator.

We have come to a point in our history when government must once against step in to preserve rights and prevent wrongs just as it did in 1964. Civil Rights are as much imperiled now as they were then. The technology revolution has undeniably brought much that is good and fruitful, but as it has evolved, this revolution has developed a dark side that concentrates increasing power in the hands of fewer people. These people control vast amounts of information. The information can tell the most of intimate of details from what we spend, what we bought with what we spend, what our daily commute is, who we may like or dislike, and, yes, our political leanings. Hardly a day goes by without some news of an intrusion into private lives which are ransacked and violated for others’ profit.

And in this context, Visa/MasterCard must be seen not merely as the hygienic facilitators of the billions of daily transactions that are the white sound of our financial life, but as an oligopoly that has converted its privileged position into political power exercised opaquely and without control or justification.

Congress should immediately investigate the imperious intrusions of Visa/MasterCard into consumers’ privacy and draft legislation that would prevent this cartel from violating their civil right to use their money as a form of speech.

Wallace Nunn is a member of the David Horowitz Freedom Center Board of Directors.