Kim Jong Un was not the only leader testing his weapons Friday night. President Trump launched a warning pardon that announced his weaponization of the Pardon Power.

Trump’s pardon of the odious Sheriff Joe Arpaio, racial profiler, torturer, and enemy of the rule of law, was a flagrant abuse of the pardon power for political gain. Trump spoke to the sizable portion of his base that thrives on anti-immigrant, racist, tough-guy messaging. The far larger impact, however, may lie in the message it sends to subjects of the Russia investigation and the further evidence it provides of Trump’s willingness to use the powers of the presidency to obstruct justice.

Trumps’ pardon of Arpaio demonstrated Trump’s willingness to fire off pardons at will, completely untethered from the broader purposes of the pardon power or the process in place to ensure that those purposes are served. Rather, he demonstrated that he views the pardon power as just another tool he can exploit to serve his immediate political advantage and, by extension, his political survival. Paul Manafort, Michael Flynn, and assorted other Trump associates and family members will sleep better knowing he has their backs. They should feel reassured that they can lie to investigators with impunity, so long as they protect Trump.

The pardon power was included in the Constitution, according to Alexander Hamilton, as a check on the possible severity of the criminal process toward individuals. Traditionally, it has been exercised when the criminal process has produced an incorrect or overly harsh result or to show mercy to the subject of the pardon because of age or infirmity. The pardon power has also been exercised to achieve a broader public purpose, generally to help the country move beyond a particularly divisive episode, as in Andrew Johnson’s pardons of Confederate soldiers, Gerald Ford’s pardon of Richard Nixon, and Jimmy Carter’s amnesty for Vietnam War resisters. Presidents exercising the power for such broader purposes have generally done so despite foreseeable political damage and they have not done so for their own legal or political advantage.

One exception – and the example most analogous to possible pardons by Trump related to the Russia investigation – was President George H.W. Bush’s pardon of six figures in the Iran/Contra scandal, including former Defense Secretary Cap Weinberger. One of those pardoned had already been convicted at trial, three had pled guilty and two, including Weinberger, were facing trial. Bush issued the pardons in December 1992, after he had been defeated by Bill Clinton and was beyond political consequences. Weinberger’s trial for lying to Congress and obstructing justice by withholding personal notes was scheduled to start in January.

Independent Counsel Lawrence Walsh’s response resonates today. He said that the pardons “undermine[d] the principle that no man is above the law.” He opined that

“Weinberger’s early and deliberate decision to conceal and withhold extensive contemporaneous notes of the Iran-Contra matter radically altered the official investigations and possibly forestalled timely impeachment proceedings against President Reagan and other officials. Weinberger’s notes contain evidence of a conspiracy among the highest-ranking Reagan Administration officials to lie to Congress and the American public. Because the notes were withheld from investigators for years, many of the leads were impossible to follow, key witnesses had purportedly forgotten what was said and done, and statutes of limitation had expired.”

Walsh also made it clear that he thought Bush had acted to protect himself. Walsh had recently discovered that Bush had failed to produce his own, inculpatory, contemporary notes of the affair. Those notes would have been featured in Weinberger’s trial. Walsh’s statement concluded with the following: “In light of President Bush’s own misconduct, we are gravely concerned about his decision to pardon others who lied to Congress and obstructed official investigations.”

Walsh’s words of outrage regarding Bush’s pardons for undermining the rule of law and contributing to obstruction of justice apply equally to Trump’s pardon of Arpaio. The pardon did not go through the Department of Justice’s rigorous process of review – a process that generally takes years and usually depends on an expression of remorse from the recipient of the pardon. Trump issued it in the middle of an ongoing judicial proceeding. Arpaio had not yet been sentenced and he would have had the right to appellate review following the sentencing. Trump truncated and negated the judicial process, which was being pursued by his own Department of Justice.

We learned over the weekend that last spring Trump approached Attorney General Sessions to ask if the investigation into Arpaio could be dropped. Sessions reportedly responded that Justice could not back off, but Trump could pardon Arpaio if he were convicted. It seems likely that Trump intended from that moment to pardon Arpaio if he were convicted. The conversation is reminiscent of Trump’s request to James Comey to back off the investigation of Michael Flynn. It provides one more piece of evidence that Trump does not acknowledge the limitations that the rule of law imposes on a president. He does not accept that individual law enforcement decisions must remain free of presidential interference and must never be made for political gain. It must remain a bedrock principle of a democracy under the rule of law that individuals will not be targeted for prosecution or excused from prosecution for political reasons. For that reason alone, Trump’s pardon of Arpaio may well become one more element in Articles of Impeachment.

But the pardon may be a precursor to impeachment in another way. As suggested, it sends a strong message to subjects and targets of the Russia investigation that they need not participate truthfully in the investigation and should not blow the whistle on Trump because Trump will pardon them in the end. Recall that a pardon must be issued after the criminal conduct has occurred, but it may come before any charges have been filed. Each lie to a federal investigator, grand jury, or Congressional committee is a new crime. To be most effective, therefore, pardons should come late in the process. Defendants may lie throughout the investigation in the expectation of a pardon in the end. Delaying pardons also allows possible defendants to continue to assert their Fifth Amendment privileges against self-incrimination. Those privileges disappear regarding federal crimes once a pardon is granted, though individuals can still assert their privileges regarding state crimes.

Trump will expose himself to allegations of obstruction of justice if he grants pardons while the Russia investigation continues. The issue will become whether he did so corruptly with the intent to impede a federal investigation. For purposes of impeachment, Congress plainly can decide in the affirmative.

If, however, he waits until the investigation is complete, particularly if he pardons individuals who have been prosecuted, the obstruction inquiry becomes more difficult. That is where the Arpaio pardon makes a difference. Assuming the reports of his conversation with Sessions are accurate, we now know that Trump is capable of forming the intent to undermine a prosecution before it takes place, relying on his pardon authority as the means of doing so. Trump sought to impede the investigation of Arpaio. When he was told that he could not, he formulated the intent to do so by issuing a pardon after the prosecution. Trump has made clear his desire to block the Russia investigation through his repeated denunciations of it as a witch hunt, his request to Comey to lay off Flynn, his request for Comey’s loyalty, his firing of Comey, and his objection to the recusal of Sessions and the appointment of Mueller. His issuance of pardons down the road in the Russia investigation would mirror the pattern of the Arpaio pardon. Congress, take note.

Bill Yeomans is the Senior Justice Fellow at Alliance for Justice. He currently serves as Lecturer in Law at Columbia Law School, and previously taught constitutional law, civil rights, and legislation at American University Washington College of Law. He also served for 26 years in the Department of Justice, where he litigated cases involving voting rights and discrimination in employment, housing, and education, and prosecuted police officers and racially motivated violent offenders before assuming a series of management positions, including acting Assistant Attorney General. For three years, Bill served as Sen. Edward M. Kennedy’s chief counsel on the Senate Judiciary Committee, and has also held positions at AFJ and the American Constitution Society.