President Trump pardoned former Maricopa County, Ariz., sheriff Joe Arpaio Aug. 25. Here's what you need to know. (Patrick Martin,Victoria Walker/The Washington Post)

That President Trump pardoned former Maricopa County sheriff Joe Arpaio surprised no one who had been paying attention. On Tuesday, he had all but said that he was going to do so, soaking up the applause from a friendly audience at a rally in Phoenix when he broached the subject.

It being expected, though, didn’t do much to lessen the surprise at its occurrence. That was in part because of the timing: dropping the news right as the most serious hurricane in half a century was making landfall in Texas on a Friday evening. But even more because of what Arpaio was being pardoned for. Arpaio was convicted of contempt of court after being told to stop racially profiling Hispanics in his county but continuing to do so anyway, in part to bolster his reelection bid. This was a law enforcement official who was ignoring a federal court order and, as a result, was convicted of a misdemeanor.

And Trump pardoned him.

The rationale Trump offered was not complicated. It came down, essentially, to the idea that Arpaio had an honorable career of service — to being the kind of guy that Trump respects.

“Throughout his time as Sheriff,” the alert from the White House read, “Arpaio continued his life’s work of protecting the public from the scourges of crime and illegal immigration.” That was the appeal to Trump on Friday and on the campaign trail: Arpaio earned a reputation as brutal and willing to push the boundaries in his opposition to immigrants in his state, and Trump liked that.

The broader question raised by the pardon, then, is where Trump would draw the line. If he’s willing to pardon Joe Arpaio for ignoring a court order in service of a political goal Trump embraces, why wouldn’t he pardon another individual he respects for similarly ignoring a demand from the court. Say, a former employee or a family member who, say, was issued a subpoena to testify before a special prosecutor?

One message from the Arpaio pardon is precisely that Trump sees his evaluation of the boundaries of legality as superior to the boundaries set by the legal system. The Constitution gives him that power. As we’ve noted before the presidential pardon is absolute. He can pardon anyone for any federal crime at any time — even before the person actually faces any charges and even if no crime actually took place. There’s nothing anyone can do about it, except to impeach Trump and remove him from office to prevent him from doing it again. (The president who replaces him might be able to revoke a recent pardon, one expert told us, but it’s far from certain.)

In other words, if any of Trump’s allies decides to tell special counsel Robert Mueller to stick his subpoena in the south side of the National Mall, Mueller can press a court for contempt charges. The person could be convicted of those charges — and then get a pardon identical to Arpaio’s.

Does anyone think that Trump wouldn’t actually do this? His former FBI director testified under oath that Trump tried to get him to drop the criminal investigation of former national security adviser Michael Flynn. If you’re willing to ask the FBI to stop investigating a crime, why wouldn’t you simply pardon the guy who they think committed it?

There’s one catch, that was explored by Eugene Volokh in June. If you are pardoned, you can’t then assert your Fifth Amendment right against self-incrimination, since you don’t face any risk of prosecution. If, for example, I were pardoned for conspiracy to commit murder in Washington, D.C., I can’t then refuse to testify against my partner in that crime, since I can’t be tried for the crime.

That said, though, the protection against self-incrimination also applies to state crimes. So Trump could pardon someone — let’s say Flynn, for the sake of this example — and Flynn could then still assert his Fifth Amendment rights if he thought his testimony might result in criminal charges in the state of Virginia (or wherever).

Again: The pardon power is absolute. There aren’t many powers in the federal government about which that word applies, but pardoning is one of them. With that power, Trump can send a message about how and where he feels the rule of law should apply. Or, more accurately, Trump can shape how and where those rules apply. He can, as long as he has that power, grant immunity to anyone he wishes for any federal crime they commit.

For a person in his position, surrounded by a federal investigation into his campaign and his business, that’s got to be appealing. And his pardon of Arpaio makes quite clear that loyalty to Trump can prevail over loyalty to the law.