The U.S. government's order for Anthropic to withdraw its most powerful artificial intelligence models has sparked a wave of criticism from both advocates and opponents of AI regulation.

On Friday evening, the San Francisco-based company announced that the US Department of Commerce had ordered it to suspend Mythos 5 and Fable 5 for "national security" reasons, without providing further details.

Unlike Mythos 5, which was unrestricted and available only to a small number of partners, Fable 5 was heavily protected to prevent any major misuse, particularly for cyberattacks or the development of chemical and biological weapons.

But Anthropic said an organisation, whose identity it didn't disclose, reported to the Trump administration that it had found a way to bypass safeguards designed to prevent Fable 5 from being used for a cyberattack.

Anthropic described the loophole discovered by this third party, identified by several media outlets as Amazon, as "narrow" and said the software vulnerabilities it exposed were "minor."

The directive applied only to access by foreign nationals, but Anthropic said it was unable to distinguish among users based on nationality and was therefore forced to take its models offline.

A government's outright ban on an advanced AI model developed by a domestic company is unprecedented.

China blocks access to the most capable Western AI models and imposes restrictions on major domestic AI companies, but those restrictions are generally built into the models before they are released.

Entrepreneur Martin Varsavsky said the implications of the order are "enormous."

Any startup "making frontier models is at the mercy of the government," he commented on X. "Therefore, the order doesn't just punish Anthropic. It changes the rules for the entire industry."

Researcher Gary Marcus said he saw the United States and China battling to a "tie" in the AI race, until Friday's government announcement.

"It didn't occur to me the Trump administration could trip the U.S. efforts from behind," Marcus said. "But it just did."

Some observers argue that Anthropic bears considerable responsibility for its predicament after it had warned for years about the risks associated with the most advanced AI models.

On Wednesday, Anthropic CEO Dario Amodei once again called for policymakers to "activate a slow and rickety policy apparatus to deal with risks and opportunities that are going to compound surprisingly quickly from here."

Several of U.S. President Trump's supporters who, until only a few weeks ago, strongly opposed AI regulation, much like the Trump administration itself, have attempted to defend the directive.

Among them are influential investor Marc Andreessen and former White House AI adviser David Sacks.

Others, however, including former Trump AI adviser Dean Ball, accused them of intellectual dishonesty, noting that they had fiercely criticised regulatory efforts under former president Joe Biden.

The pro-regulation group Americans for Responsible Innovation argued that decisions of this magnitude should not be made "impulsively" or be subject to "political favoritism."

Anthropic is currently at odds with the Trump administration, which has terminated all of its government contracts with the company.

Many observers agree that AI has entered a new era requiring greater government involvement, but they strongly objected to the manner in which the action is carried out.

"In a functioning administration, nobody would have ever been blindsided by an action like this," said Ben Murphy of the Institute for Progress, a think tank focused on emerging technologies.

"The government simply would have just requested that Anthropic do additional testing or add more safeguards before release," he wrote on X.

AI's rapid acceleration and the concentration of influence in the hands of a few companies have caught governments off guard, said Mona Sloane, a professor at the University of Virginia.

That means that "it is possible that we will see" government-imposed suspensions of AI models again, she said.