Some government actions can discourage or “chill” speech. Donald Trump’s tweet storm this week criticizing Amazon head Jeff Bezos may be seeking to chill speech.

Trump argues that the U.S. Post office is subsidizing Amazon’s deliveries. We need not decide whether Trump or Amazon is right about this matter. The subsidy may not be the issue according to the Wall Street Journal:

Fueling Mr. Trump’s ire is not so much Amazon, the online giant that is revamping the retail industry, but the company’s Chief Executive Officer Jeff Bezos, who also owns The Washington Post, people close to the White House say. Mr. Trump sees Mr. Bezos’s hand in newspaper coverage he dislikes and is lashing out at Amazon as a proxy, these people said.

The Journal notes that the criticism arose from specific Post stories:

The president’s most recent flurry of tweets targeting Amazon has coincided with publication of Washington Post stories he dislikes. Over the past week, Mr. Trump has privately complained about two particular Post stories, White House aides and others said: a March 30 article that documented problems at a White House office that vets political appointees and another the following day that depicted Mr. Trump acting more independently of chief of staff John Kelly and other “moderating forces.”

So what, you might think. The president has a right to free speech too, and Bezos is not in jail. If Bezos can’t stand the heat, as the saying goes, he should stay out of the DC kitchen.

But therein lies the free speech problem. Bezos could get out of Trump’s kitchen by telling the editors and reporters at his newspaper to shut up about the President. That would be a classic case of the “chilling effect” of government threats on political speech.

Why would Bezos do that in response to mere criticism by Trump? It’s not as if Trump is an authoritative public figure whose views garner widespread respect. Trumpian attacks might even increase Bezos’ public standing.

But investors might well believe that Trump will follow his criticism with actions to harm Amazon. For example, the administration might reward a $10 billion defense contract to one of Amazon’s rivals. (To be fair, Trump apparently told one of those rivals that the decision was not his to make). The president also appoints the Postal Service governing board that sets postal rates. Any president will have many other ways to harm a critic, especially one whose successful business interacts often with government policies. For these reasons investors might think Amazon had become less valuable after Trump’s tweeting. Indeed Amazon fell 7% and lost close to $60 billion in market value in the week after the public learned that Trump wanted to “go after” the company.

This whole sorry affair suggests two points, one libertarian, one not so much. The U.S. president stands at the top of a powerful federal government. He has wide discretion over that federal power. Some believe that a benevolent president can use such power to instill “energy to the executive” and improve the world. But a vindictive man overly sensitive to criticism can also use presidential power to harass his critics.

Libertarians focus rightly on the rule of law, but not all restraints on power are written in formal rules. Informal norms can also constrain public officials. We might expect, for example, that an elected official would not directly threaten the value of a business to silence a critic. That expectation appears rather naïve. We may be entering a time when free speech is less free both because it is more threatened and because more sacrifices will be necessary to protect it.

Jeff Bezos is not in jail, but he is lighter in the wallet, at least for now. Will his speech be chilled by this illiberal president? There are reasons for hope. Post officials deny that Bezos intervenes in their coverage of the White House. Amazon is a popular company. Attacking him may not be popular beyond Trump’s base. Bezos built Amazon. He cannot be a weak man given to giving in to bullies. Much depends on what he does next.