Eric Posner is a professor at the University of Chicago Law School. He is co-author of "Radical Markets: Uprooting Capitalism and Democracy for a Just Society," to be published in May.

It is by now conventional wisdom that President Trump is an authoritarian. But as we embark on the second year of his term in office, we would do well to think carefully about which of his actions have actually violated the Constitution. And it turns out that, so far, Trump has used his powers less aggressively than most modern presidents. That doesn't mean he's a good president. In fact, it probably means he's a bad one.

David Frum's new book, "Trumpocracy: The Corruption of the American Republic," is only the latest statement of the case that Trump is a danger to the Constitution. But it is critical to distinguish Trump's bark from his bite. He has disparaged judges, called the media the enemy of the people, praised torture and compared the intelligence community to Nazis. But he has not followed up on these statements. Unlike Franklin D. Roosevelt, he hasn't tried to pack the Supreme Court (not that Trump needs to). Unlike Barack Obama, he hasn't (yet) targeted journalists in leak investigations. Unlike George W. Bush, he hasn't actually taken a page from the Nazis by ordering the intelligence community to use coercive interrogation.

VIDEO: What a presidential president would have said the day of the Charlottesville unrest (Gillian Brockell/The Washington Post)

What has Trump done? He has tried to stop various groups from entering the country, with a focus on migrants from Muslim- ­majority countries and refugees. While the courts have blocked some of his efforts, the legal basis for these actions was hardly outside the mainstream, and he may yet win in the Supreme Court. Many presidents have blocked migrants from entering the country, or even expelled them, as Bush did to Arab and Muslim groups after the terrorist attacks of Sept. 11, 2001. The important thing is that Trump has obeyed the courts' decisions. All presidents lose in the courts, sometimes frequently, and then grumpily comply with the rulings. Trump has been no different.

Trump has also announced that, unless Congress acts to protect them, he will make the "dreamers" again subject to expulsion. But here, too, he has acted within the law. The decision by Obama to give papers to these young immigrants sparked criticism on legal grounds, even from many people who supported the policy. A subsequent immigration action by Obama that deferred action for another group of migrants was blocked by the courts.

Trump's comments in the aftermath of a white supremacist demonstration in Charlottesville angered many people, but presidents are allowed to say what they want. He fired some missiles into Syrian territory, which some people think was an abuse of power, but this was no different from actions taken by Obama, Bill Clinton and many other presidents.

The president withdrew the United States from the Paris climate treaty, but the treaty was nonbinding. His efforts to reduce cooperation under international trade agreements also fall within his legal authority.

Trump has also issued executive orders to control regulation and centralize regulatory authority in the White House, following the footsteps of every president since Ronald Reagan.

Trump's financial conflicts of interest are troublesome. They may well be illegal. But until a court says so (some cases are pending), we need to reserve judgment. He may well divest assets if a court orders him to. He should have disclosed his tax records, but broke no law by failing to do so.

Finally, there are the actions surrounding his campaign. Trump may have violated the law, but until we hear from special counsel Robert S. Mueller III, we don't know. He did not violate the law by removing James B. Comey as the FBI director — unless he did so to obstruct justice. We'll also need to wait for Mueller to tell us whether a compelling case can be made for that. The new revelation that Trump sought to fire Mueller in June is certainly alarming, but the president backed down when his White House counsel threatened to resign. Not all that long ago, another president — Bush — backed down when Justice Department officials (including Comey and Mueller, confusingly enough) threatened to resign over Bush's constitutionally questionable domestic surveillance program. But even if Trump fires Mueller, there is no constitutional violation unless he does so to obstruct justice.

Nonetheless, Trump is regarded in many quarters as the greatest threat to our constitutional system of, perhaps, any president in history. The view is understandable. Trump has recklessly criticized virtually all the institutions that constrain the presidency, while expressing admiration for dictators such as Vladimir Putin of Russia.

How do we account for this disparity between bark and bite? Three explanations come to mind. First, Trump is a blowhard and a bully. But like most bullies, he is also a coward. He tries to intimidate people, but cringes when people stand up to him.

Second, Trump is trying to lay groundwork for an attack on our institutions at a politically opportune moment. He might think that if he damages the prestige of the courts, he can defy the Supreme Court if it ultimately rules against the travel ban. Or that if he gets everyone to hate the media, he will be able to prosecute journalists.

Third, Trump maintains support from his base by supplying it with rhetorical red meat, while at the same time avoiding fights that he might lose. The base is angry with Washington, and so thrills to Trump's fulminations. But Trump realizes that it will ultimately not forgive him if he doesn't accomplish anything. That requires cooperation with the other branches within the constitutional framework.

Prudence suggests that we should worry about the second explanation. But we also need to recognize the difference between words and actions, especially in a president who seems to model himself on characters at WrestleMania. Trump's reckless words have damaged his public standing, here and globally, and have aroused distrust in Congress, the courts and the media, hampering his ability to advance his agenda. The result? He probably will be stopped if he tries to violate the Constitution. And his presidency probably won't accomplish anything of value.

Read more on this issue: