In September, I identified four myths that dog discussions about presidential impeachment. Perhaps the most persistent and surprisingly consequential of these myths is the notion that impeachment and removal decisions amount to pure politics, as opposed to a set of legal determinations made by a political branch.

How has the false dichotomy between the political and the legal proven important? In 2017, we saw elaborate efforts to articulate hard limits on Congress’s impeachment and conviction powers that, in my view, reflect reluctance to recognize the legal dimensions of Congress’s assessments in this realm and the quasi-judicial aspects of Congress’s role in making these assessments. On a related note, many commentators have been quick to dismiss the legal utility of congressional involvement by assuming the legal validity of Trump’s use of his broad powers. For example, within hours of Trump's pardon of Joe Arpaio, the Arizona sheriff, Adam Liptak declared in the New York Times that the pardon was “almost certainly lawful” because “there is nothing in the text of the Constitution’s pardons clause to suggest that he exceeded his authority.” Some months earlier, in the pages of New York Magazine, Jonathan Chait made the same assertion and, using similar logic, agreed with Trump that the president had “a legal right to fire FBI Director James Comey.” These sorts of pronouncements write off the potential complexities of ascertaining constitutionality and, in exceptional circumstances, the need for a congressional inquiry to satisfactorily deduce presidential motive or other factors that may be relevant to distinguishing a permissible exercise of authority from an impermissible abuse of power.

Perhaps because we are so accustomed to thinking of the courts alone as the last word on the law, we are underrating the challenges inherent in evaluating presidential misconduct, as well as Congress’s capacity (and obligation) to meet those challenges with the necessary findings of fact and rulings of law in the event of an impeachment inquiry. That’s unfortunate, because when it comes to misbehaving presidents, the House and Senate have indeed been vested with the say-so—and attendant authorities—that we generally attribute to the judiciary. The House may charge the president with impeachable offenses and the Senate may try him: that is, probe his conduct, question witnesses, collect evidence, and take a range of investigatory steps on certain sensitive subjects normally within the executive’s purview. This is not to say that Congress has every one of the tools available to the prosecutor pursuing an ordinary criminal investigation or the stomach to exercise the tools it has; as Bob Bauer has cogently explained, Congress has demonstrated some investigative deficiencies that make it all the more important for the Mueller investigation to proceed unimpeded. But my modest point is that Congress is vested with the authority to determine, as a legal matter and not as a political antic, whether the president has committed a misdeed for which he may be impeached.

In an interesting recent three-part series for Lawfare, Josh Blackman set out a formalistic theory of impeachment constraints that I think commits the error of minimizing the juridical implications of Congress’s power to charge, try and convict the president for impeachable offenses. He begins by asserting that the Constitution’s “negative limitations on Congress’s powers and positive vestings of power to the president” cabin what can constitute an impeachable offense. Applying this rule, he reasons that “President Trump’s firing [of] James Comey is supported by both the positive grant of authority over foreign affairs, and is enabled by the negative restrictions on Congress’s power over the removal of principal officers.” He concludes that Congress cannot impeach Trump for the firing.

I have no quibbles with one part of this theory: If the Constitution prohibits Congress from doing something, such as making a law restricting speech, then Congress can't turn around and regulate the president on the prohibited basis by treating what should be permissible conduct as a ground for impeachment. This is a line of argument already put forward by other impeachment scholars, like Charles Black, who famously explained that general constitutional prohibitions on ex post facto laws and bills of attainder limit the universe of conduct for which Congress could impeach the president. Congress may not enact a law making past conduct criminal; in the same spirit, Congress can't impeach a president as it pleases for conduct that a reasonable man would not think abusive and wrong.

But Blackman takes things in another direction when he insists that some of Trump's actions, like Comey’s firing, are entitled to “constitutional immunity.” Blackman explains that when it comes to the president's exercise of powers that are exclusive to the executive, the president is insulated from criminal prosecution or impeachment, whatever his actual reasons for so acting.

I think this is wrong. Though Congress may not turn impeachment into a fishing expedition, there are no realms of impunity and no exercises of power that can be meaningfully described as categorically exempt from serious congressional scrutiny. Just about any of the president’s Article II powers could be abused in such a way as to amount to an unconstitutional action and impeachable offense. The potential for abuse (and hard-to-anticipate forms of abuse, at that) is in the nature of great power, and an impeachment inquiry is our Constitution’s answer to this reality. Contrary to Blackman’s assertions, Trump cannot offer the shambling semblance of an Article II excuse for what is, on its face, deeply problematic conduct—like firing Comey and publicly conceding that the firing was related to the Russia investigation—and then claim Congress is constitutionally obliged to leave him be.

It may be that Congress will not be able to answer questions about whether the president has committed the kind of breach that rises to the level of an impeachable offense without looking into the president’s mindset. This is cause for concern but not despair; courts conduct this sort of probe all the time. As Black put it in his 1974 impeachment handbook, “courts have to try, and continually do try, to work out the truth about intents and motives, for these are often (in bribery cases as elsewhere) of the very essence of the charge.” Similarly, Congress may need to take up this set of challenges when serving as the rough equivalent of a grand jury and then a tribunal for impeachment and removal purposes. Black expressly acknowledged the difficulties, rather than suggesting Congress could or should shy away from them:

Is it “bribery” (or attempted “bribery”) to suggest to a federal judge, engaged in trying a case crucial to the executive branch, that the directorship of the Federal Bureau of Investigation might be available? It is not wrong to offer a good district judge an important job. Almost all district judges, almost always, have government cases pending before them, in some number. Again, it is motive or intent that is crucial and that is hard to prove.

The pardon power—almost absolute on its face where it appears in Article II, Section 2—makes for some easy illustrations of just how essential it is for Congress to be able to examine presidential intent or motive in an impeachment case involving what might otherwise look like a facially valid exercise of executive power. Imagine the president pardoned Arpaio in exchange for $1 million in cash. Could Trump be impeached for the pardon? Of course—this is bribery, and Congress has been vested with the power to impeach and remove him for it. Imagine the president granted a set of pardons to assist a foreign adversary in waging war against the United States. Could he be impeached for the pardons? Of course—this is treason, and Congress has been vested with the power to impeach and remove him for it. Imagine the president were to “announce and follow a policy of granting full pardons, in advance of indictment or trial, to all federal agents or police who killed anybody in line of duty, in the District of Columbia, whatever the circumstances and however unnecessary the killing.” Could he be impeached for his pardon policy? Of course—like Black, who proposed this hypothetical back when it was impossible to imagine a president capable of such a thing, I think this is unquestionably a high crime or misdemeanor, and (say it with me) Congress has been vested with the power to impeach and remove him for it.

A corollary to all of these conclusions is that Congress must have some room to prod a disturbing pardon decision, notwithstanding the seemingly limitless and obviously exclusive nature of the president’s pardon authority. As Benjamin Wittes recently wrote on the subject, “good faith matters.” Because it matters, the power to ascertain when the president is far adrift of shore is part and parcel of Congress's impeachment function.

Precedents regarding the division of power between the two political branches should not be confused with absolute limits on Congress’s ability to inquire into presidential abuse of power in the impeachment context. For example, Blackman argues that the president’s exclusive recognition power as described by the Supreme Court’s 2015 decision in Zivotofsky v. Kerry puts a “limitation on the scope of what can constitute a ‘high Crime.’” Invoking “the eternal words of Justice Robert Jackson,” he writes, “Because the president’s power here is ‘exclusive,’ ... it ‘disables the Congress from ... impeaching the president on that basis.’”

If Blackman is arguing that the president cannot be impeached for his use of the recognition power, he is incorrect. The fact that a power is exclusive to the executive—that is, the president alone may exercise it—does not mean the power cannot be exercised in clear bad faith, and that Congress cannot look into or act upon knowledge of that abuse. Again, as Daniel Hemel and Eric Posner have pointed out, bribery makes for an obvious (but far from the only) counterargument. Could the House impeach Trump if there were suspicions that he recognized Jerusalem as the capital of Israel in exchange for a suitcase of money? This scenario makes clear the president could not claim a blanket exemption from charges that he misused a power exclusive to him, but we can imagine others. Of course, like any court, Congress is limited to lawful bases for its actions when sitting to impeach or convict; Congress cannot impeach the president for recognizing a foreign nation just because Congress does not agree with the president’s foreign policy agenda, any more than a court could settle a case by flipping a coin or reading entrails (to borrow Philip Bobbitt’s tidy rejoinder to anyone who would argue that as Americans we do not share a common legal grammar). But that is a legal restriction on impeachment implicit in the constitutional requirement that the president commit bribery, treason, or a high crime or misdemeanor in order to be subject to impeachment. That restriction cannot be meaningfully characterized as creating a species of presidential immunity. If you disagree on the ground that bribery is just a special exception to what might otherwise constitute a realm in which the president enjoys immunity, then the same must be said for treason, as well as the more expansive and indeterminate bucket of “high Crimes and Misdemeanors.” These exceptions sap the supposed realm of “constitutional immunity” of any meaning.

The bottom line is that there is no avoiding the difficult, fact-specific question of what constitutes a high crime or misdemeanor by way of one-stop immunity rules about impeachment-proof exercises of executive authority. Arguing that there are zones of executive authority that Congress may not probe or whole categories of executive conduct for which Congress cannot impeach requires ignoring the parallel mechanism that beats blood through our constitutional power structure: presidential authority comes with concomitant presidential obligations, and in the impeachment context, Congress has significant power to protect against a president’s attempts to use the former for the purpose of flouting the latter.