Donald Trump, with both words and deeds, is presenting a new theory for presidential power since being impeached by House Democrats but acquitted by Senate Republicans.

In one of his most brazen threats yet, the president on Friday morning told the world he is poised to burn down a norm that has long allowed the Justice Department to operate mostly without political influence.

Mr Trump fired off a tweet quoting his hand-picked attorney general, William Barr, in a Thursday interview with ABC News when he pushed back on other presidential tweets which weighed in on agency business or floated what many have interpreted as director orders. After all, the White House has never altered former Press Secretary Sean Spicer's announcement that tweets from Mr Trump's personal account are official government statements.

"'The President has never asked me to do anything in a criminal case,'" the president wrote, misquoting his AG.

Here is the full Barr quote from his explosive ABC interview: "And I'm happy to say that, in fact, the president has never asked me to do anything in a criminal case."

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But Mr Barr wasn't finished, adding: "However, to have public statements and tweets made about the department, about our people in the department, our men and women here, about cases pending in the department, and about judges before whom we have cases, make it impossible for me to do my job and to assure the courts and the prosecutors in the department that we're doing our work with integrity."

Mr Trump excluded that part of Mr Barr's comments in his tweet, opting instead to add a section to what amounts to his post-acquittal thesis on presidential powers.

"This doesn't mean that I do not have, as President, the legal right to do so, I do," the president of the United States wrote, "but I have so far chosen not to!"

It often can be tempting to read too much into Mr Trump's tweets. But on Friday, the opposite appeared the case. After his Tuesday morning tweet that appeared to pressure Justice Department officials into softening their sentencing recommendation for longtime pal and adviser Roger Stone, followed by them doing so and him denying it, followed by a seeming admission he did indeed apply pressure, it would be tempting to view the Friday morning post through a Stone-centric lens.

But a closer look, while also viewing the tweet in the context of his post-acquittal revenge tour, and Mr Trump appeared ready to expand the scope of the presidency.

That's because he was threatening to not just tip the balance of justice in the Stone sentencing process, but any other criminal matter he might choose – be it one a member of one of his plush clubs brings up during dinner or another mentioned on Fox News.

To be sure, there is no law preventing a president from doing exactly what Mr Trump suggested. But there are limits in place.

"The Constitution grants the president substantial, but not unlimited, judicial powers," said Mark Rom, a Georgetown University professor. "The president can offer pardons, but cannot indulge in jury tampering, for instance."

From his office's war powers to its ability to punish administration officials he believes betrayed him during the impeachment process to his actions and threats to the justice system, Mr Trump's actions are part of a broader trend, according to one expert.

Ivan Krastev, chairman of Centre for Liberal Strategies, sees Western democracies at something of a tipping point, similar to where the global economy teetered in 2008, at the peak of the Great Recession.

"From this point, populism can be destructive," he told the Munich Security Conference on Friday.

"We are going to be much more shattered" unless certain institutions inside democratic governments are walled off from the whims of populists like Mr Trump and others who have gained power in Europe, Mr Krastev said, adding: "We have slightly forgotten all the things ... that are part of democracy."

Speaker Nancy Pelosi, speaking at the same conference in Germany, noted that "in America, we have many people who have fled autocratic systems."

"They have experienced it. ... They bring a different kind of wisdom to making judgements to falling prey to some kind of ... nationalistic argument," the California Democrat who made the final call on starting the impeachment process said on Friday.