President Trump's pardon of Joe Arpaio, though completely lawful, will have unfortunate collateral effects on the separation of powers.

First, as a matter of raw executive power, the Constitution imposes no limitations on whom the President can pardon—only that the "offences [be] against the United States" and that the pardon be accepted. In that limited sense, there is nothing problematic about Trump's pardon. That’s the easy part, which we can quickly dispose of. But the inquiry hardly ends there.

Second, the timing of the pardon is entirely premature. As a threshold matter, Arpaio had been convicted, but not yet sentenced. In the event that the district court's judgment was in error (and as far as I can tell, it understated the Sheriff's numerous violations of the rule of law), Arpaio had the potential to appeal to the 9th Circuit Court of Appeals, and ultimately the Supreme Court. It was entirely feasible the Sheriff would not be sentenced to any jail time. Here, Trump’s preemptive pardon short-circuited the judicial process. Indeed, according to reports, Trump had earlier inquired of the Attorney General Sessions about simply dropping the prosecution before it even came to a final judgment. In another illustration of the Solitary Executive, Sessions apparently refused. Trump did not seem to mind, because he had already determined that he would grant clemency after the conviction.

Third, the manner in which Trump issued this pardon sets a dangerous precedent. I had previously hoped that the Pardon Office within the Justice Department would prevent such reckless behavior, but here, once again, the Solitary Executive acted completely unilaterally within his own administration. As a constitutional matter, the pardon power belongs to the President, and the President alone. If Trump wants to reverse the processes established by his predecessors, that is entirely within his prerogative. But the Executive Branch had imposed long-standing institutional constraints on that awesome power with very good reason. Here, Trump has untied himself from the mast, retweeted the Sirens' call, and crashed into the shoals.

Shortly before the pardon was issued, an unnamed attorney in the White House Counsel’s Office asked Arpaio's lawyer whether he would accept the pardon; he agreed. "A few minutes later," the Washington Post reported, "an email arrived from the White House with a single page attachment: an 'Executive Grant of Clemency' for Arpaio signed by Trump in his thick, black script, complete with a golden Justice Department seal." There is a cost to bypassing the usual process. Unlike other controversial acts of clemency—such as George H.W. Bush's detailed pardon of members involved in the Iran-Contra affair—Arpaio's pardon lacks any rationale as to why clemency was warranted, other than Arpaio’s patriotism and advanced age. The lack of reasoning diminishes the pardon’s legitimacy.

Fourth, this decision will inevitably spill into the courts. Since shortly after the inauguration, I have mounted an at-times lonely defense of the principle that courts should not modify their jurisprudence in response to Trump's norm-busting behavior. This latest pardon, I suspect, will hit closest to home for Article III judges. At bottom, the pardon amounts to an executive nullification of a district judge’s finding of criminal contempt of court. There is no allegation that the district court erred, or that Arpaio was the victim of a miscarriage of justice, or that the sentence was unjust (for, indeed, no sentence had even been imposed). To the contrary, as far as I understand, most of Arpaio's most egregious conduct will go unpunished. Combined with his frequent attacks on the judiciary, this latest episode will no doubt harden Pharaoh's proverbial heart. The consequences are predictable. This coming term at the Supreme Court is shaping up to be an incredible blockbuster season, with decision after decision affecting the scope of the President's powers. The Solicitor General’s task becomes even more intractable as a result of this presidential action. Further, lest we forget, Justice Anthony Kennedy's decision about whether to retire or not may well be conditioned by the current state of affairs at term’s end.

Fifth, Congress should not stay silent. Far short of bringing articles of impeachment, Congress has many options at its disposal. This week, Benjamin Wittes and Jane Chong suggested that Congress should open an impeachment inquiry into President Trump's behavior. There are less drastic options available too. Officials from the executive branchcan be asked about the process that gave rise to the Arpaio pardon. Committees can hold hearings on the matter. Even if Republicans are hesitant to openly oppose the President, they can take steps to express their displeasure with the pardon, beyond mealy-mouthed tweets.

Sixth, I am doubtful that this pardon will bring a close to L'affaire de Arpaio. Trump's clemency only extends to federal offenses. Prosecutors in Maricopa County have the full wherewithal to bring state-law criminal charges against the former Sheriff. Likewise, civil litigation remains a viable option to seek damages from him. There is also rumbling on a major constitutional law listserv that a contempt conviction—premised on the inherent powers of the court—may not be subject to the pardon power. In the normal course of business, I would dismiss this sort of off-the-wall idea, but, going back to my fourth point above, I can imagine ways that the validity of a pardon could be collaterally challenged, particularly in courts receptive to a Trump-is-different jurisprudence. For example, civil litigants in a future Section 1983 action could seek to introduce evidence of the conviction in a court proceeding, at which point Arpaio would argue that the conviction was nullified. A court could then purport to adjudicate the pardon’s legal legitimacy. (Beyond the constitutional issue, there is a question of whether evidence of the pardoned conviction would even be admissible.) In any event, this saga is far from over.

Finally, I worry what precedent this decision sets for the future. Trump's decision to use the pardon power to bypass the judicial process does not bode well for the Mueller investigation, as the President could preemptively pardon everyone in his inner-circle, or even himself. Moreover, Presidents generally defer controversial pardons untilthe ends of their administrations when no one is paying attention. Trump's first pardon came less than eight months into this presidency, and it went to a sheriff who consistently flouted court orders. This is the beginning, not the end.

Perhaps the next President will abandon all manner of Trump's outlandish behavior. But, alas, Article II is something of a one-way ratchet. Obama built on Bush, who built on Clinton, who built on Bush, and so on. Each President does not readily abandon the power aggrandized by his predecessor. The 46th President, whomever he or she will be, will inherit what Justice Robert Jackson famously referred to as "a loaded weapon, ready for the hand of any authority that can bring forward a plausible claim of an urgent need." We can only hope the trigger is not pulled.