The evidence forms a high stack. U.S., European and other companies are selling technologies that enable the repressive Iranian and Syrian regimes to disrupt and monitor the Internet and track down government critics, as documented in media reports, notably by Bloomberg News.

On Monday, President Barack Obama acted. He issued an executive order giving the Treasury secretary the power to sanction individuals and companies that provide goods or services that can be used for such purposes. Those with assets in the U.S. risk having them blocked; individuals without such assets can be barred from entering the country. Perhaps the greatest penalty is the reputational cost of being placed on a U.S. sanctions list.

The order is a powerful new tool. By covering direct and indirect sales, it addresses the excuses some companies have given when confronted with evidence of their wares in Iran and Syria. They can no longer hide behind claims that goods sold to a legitimate middleman were then resold without a company’s knowledge, as the U.S.-based Blue Coat Systems Inc. did after its technology was found filtering websites in Syria.

Moreover, the order encompasses technology that is even “likely” to be used to monitor and track citizens through their online activities. In other words, companies should err on the side of caution when selling the Iranians or Syrians anything dubious.

Of course, it’s good for citizens of these countries to have access to online communications. Western providers have been and should be helping to create those infrastructures, even though the regimes can add tapping capabilities to them.

When it comes to add-ons, however, Iran and Syria are not like other places. A system that can track down lost mobile phones is nice for consumers. But brutish security forces can also use it to hunt for pro-democracy activists. Spam-filtering technology can help keep mobile networks running faster, but in Syria it has also allowed government officials to block all messages including words such as “revolution,” “demonstration” and “strike,” thus interfering with freedom of expression and assembly. In these countries, the risks of such systems outweigh the benefits. Decent companies have no business selling, installing or maintaining them.

Issuance of the president’s order alone is unlikely to make them desist. Company executives may doubt the government’s seriousness about enforcement. After all, the U.S. already had a rule barring federal agencies from doing business with companies that export to Iran any technology used to disrupt, monitor or restrict the speech of Iranians. When the Government Accountability Office produced its report on such companies last June, it came up with none, though soon after journalists detailed several.

The glare of news media exposure has been enough for a couple of companies to pull out of their contracts in Iran and Syria. If the Treasury Department were to pursue one or two remaining cases, it would pressure those companies that still provide questionable technologies.

Because the executive order puts the onus on companies to know where their goods end up, many will need to introduce new diligence to their systems. For instance, companies can scan the Internet addresses of prospective buyers and their existing customers to check for Iranian or Syrian locales. And, any Internet-connected product can be set up to periodically ping its manufacturer — that’s how software updates work — and provide location information.

Voluntary groups such as the Global Network Initiative are exploring new ways for companies, investors, human-rights groups and academic experts to minimize the potential for human-rights abuses while maximizing the spread of communications technologies. Their success will shape future U.S. legislation, some of which contemplates the imposition of a potentially onerous export control regime. For a medium that thrives on freedom, it would be unfortunate if the heavy hand of some states could only be redressed by that of another.

By David Shipley