A little over a week ago, seven former Directors of the Central Intelligence Agency sent a letter to the President of the United States urging him to reverse Attorney General Eric Holder’s decision last month to appoint a special counsel to investigate the conduct of CIA interrogators during the Bush administration.

This letter has reopened the policy argument over whether Holder’s decision is consistent with the public interest. The former CIA heads contend that such an investigation will foster undue caution in current CIA officers, who will inevitably fear that their actions might be prosecuted by a later administration, and will undermine intelligence cooperation on the part of foreign powers, who will inevitably fear that such cooperation might be publicly revealed in a subsequent investigation.

In contrast, supporters of Holder’s decision argue that such an investigation will bolster the reputation of the United States and hence enhance its security by demonstrating to the world that it rejects and will punish unlawful and inhumane methods of interrogation. The controversy over the letter has also, however, revealed a widespread and highly placed misunderstanding of the nature of the attorney general’s duty and his relationship to the president. And while the debate over the prudence of Holder’s investigation will rightly continue, this constitutional misunderstanding should also be addressed.

In effect, the seven former CIA heads contend that Holder should not have made the decision that he made and that the president should accordingly intervene and overturn that decision. In response, the supporters of the interrogation investigation not only defend it on its merits but also advance a kind of procedural argument that holds, remarkably, that neither the attorney general nor the president, two of the highest ranking public officials in the United States, has any choice in whether to proceed with such an investigation. For example, in responding to the CIA chiefs’ letter, Jameel Jaffer, the director of the American Civil Liberty Union’s National Security Project, argues as follows:

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The suggestion that President Obama should order Attorney General Holder to abort the investigation betrays a misunderstanding of the role of the attorney general as well as the relationship between the attorney general and the president. Where there is evidence of criminal conduct, the attorney general has not just the authority but the duty to investigate. The attorney general is the people’s lawyer, not the president’s lawyer, and it would be profoundly inappropriate for President Obama to interfere with his work.

This defense of the investigation  reveals a serious misconception of the authority and duty of both the attorney general and the president—and hence of the very rudiments of America’s system of constitutional government.

Let us leave aside the astonishing confidence of Mr. Jaffer’s assertion that a bipartisan group of seven men who served capably at the highest level of the executive branch have fundamentally misunderstood the character of the president’s authority and that of the attorney general. Let us instead examine, first, his claim that the attorney general has a “duty” to investigate where there is “evidence of criminal conduct.” This statement, while true in a general sense, nevertheless mischaracterizes the specific nature of the present case. To begin with, Attorney General Holder did not simply order an investigation into the legality of some past CIA interrogations; he in fact went so far as to appoint a special prosecutor to conduct that investigation. To be sure, the United States has seen numerous special prosecutors over the last four decades, and there is nothing necessarily improper in an attorney general’s decision to appoint one. Nevertheless, it is worth remembering that such investigations are rare and a departure from the manner in which almost all federal crime is investigated and prosecuted. Ordinarily, inquiry into alleged criminal conduct is handled by divisions of the Justice Department that are charged with the investigation and prosecution of certain kinds of violations of federal law. In contrast, a special prosecutor is charged with the investigation of a certain set of specific possible violations alleged to have been committed by a certain set of specific individuals. While such an extraordinary method of investigation may be justifiable in some cases—and while it could even be appropriate for the interrogation inquiry—the decision of whether to adopt it is the free decision of the attorney general and not something he is required by law to do.

For a time in American history there was a statutory mechanism by which an attorney general could be legally required to appoint the equivalent of a special prosecutor: the Independent Counsel Provision of the Ethics in Government Act, which was created in response to President Nixon’s firing of a special prosecutor investigating the Watergate scandal. In the wake of the independent counsel investigation of President Clinton, however, Congress allowed this provision to lapse, and it is no longer a part of federal law. Attorney General Holder’s decision to appoint a special prosecutor, then, is properly understood as an exercise of his discretion and judgment and not as something he is simply duty-bound to do.

Moreover, contrary to Mr. Jaffer’s suggestion, Eric Holder has no official obligation to order even an ordinary investigation into CIA interrogations. Mr. Jaffer contends that the attorney general “has not just the authority but the duty to investigate” when there is “evidence of criminal conduct.” This is accurate as a general statement of the attorney general’s job. It is not necessarily true, however, as applied to any specific case, and it cannot be an adequate justification for authorizing any particular investigation. No government prosecutor has sufficient resources to investigate every alleged criminal act that is brought to his attention. Prosecutors therefore have, and have always been understood to have, a legitimate discretion to decide which cases to investigate and which to leave alone. They must use their own judgment to answer this question, usually by asking which cases involve more serious violations of law and which ones carry a good chance of successful prosecution should the matter come to trial. Either of these considerations could reasonably justify a decision not to pursue the interrogation investigation.

Indeed, a prosecutor may sometimes have good reasons not to pursue a case even when it involves serious wrongdoing and has a good chance at trial.  Any criminal act is presumptively a harm to the public good. Yet it is equally true that some investigations can be more harmful to the public good than the crimes into which they inquire. Such an argument was understood and publicly defended by no less a proponent of the rule of law than John Locke, who, in his Second Treatise of Civil Government, noted that those charged with the execution of the law may sometimes choose to leave a crime unpunished for that sake of the public welfare. This is precisely the kind of argument being urged by the former CIA chiefs, and it is certainly one that the attorney general could properly consider.

Mr. Jaffer errs not only in contending that duty compels such an investigation, but also in claiming that “it would be profoundly inappropriate for President Obama to interfere with” the attorney general’s decision to launch it. This error has also been propounded by White House officials, who reportedly have claimed that the president “has no right to interfere with the Justice Department’s work,” and even by Senator John McCain who, while criticizing Holder’s decision, has nonetheless conceded that the “attorney general has a unique position in the cabinet” such that he “obviously . . . can’t be told what to do by the president.” This misunderstanding has been advanced for several decades by various highly placed figures, but it is no less incorrect for all that. When President Nixon fired his attorney general and several top Justice Department officials in order to get rid of the special prosecutor pursuing the Watergate affair, some in the news media presented his action as creating a “constitutional crisis.” During the recent Bush administration, some commentators spoke as if the president acted illegitimately when he rejected the legal findings of the Justice Department’s Office of Legal Counsel and preferred instead the advice of the legal advisers to the vice-president, or when he dismissed some U.S. Attorneys for failing to pursue some cases. Such presidential decisions may have been mistaken, and in some cases they might even have constituted abuses of the president’s power, if they were motivated by personal or partisan considerations. Yet none of these actions can reasonably be considered inappropriate in the sense of being beyond the President’s power, for the simple reason that they all manifest the president’s undoubted command of the executive branch of government. Under the Constitution, the president is the nation’s chief executive. He is the head of the executive branch, that part of the government that executes or enforces the law. Accordingly, it is the president, and not the attorney general, who is the country’s chief law enforcement officer. And while all officers charged with the enforcement of the law possess the discretion discussed above, that discretion is subject to the control and correction of their superiors in the executive branch who must also exercise their own discretion in supervising the work of their subordinate officers. That is why the president has a perfectly unobjectionable authority to remove Justice Department officials for what he regards to be their mistaken judgments about what cases to pursue or not to pursue, and why he can properly choose to reject the legal advice of the Justice Department if he thinks it is erroneous. It is also why, in the present case, Attorney General Holder had a right to reverse the decision of subordinate officials not to pursue the interrogation investigation, and accordingly why the president could properly, if he thought it best, order the attorney general to reverse himself.

Finally, Mr. Jaffer’s argument is inconsistent not only with the basic structure of the executive branch, but is also inconsistent with itself. Again, in defending the investigation, he contends that the “attorney general is the people’s lawyer, not the president’s lawyer, and it would be profoundly inappropriate for President Obama to interfere with his work.” Once more, this is a true remark that is irrelevant to the matter at issue. Of course the attorney general is a public official, and no one would think it proper for the president to use him for his personal legal business. Taken in the sense Mr. Jaffer intends it, however, his remark becomes incoherent. How can one claim that the attorney general is the people’s lawyer and, at the same time, insist that he is in no way answerable to the sole executive official, the president, who is himself answerable to the people? It would be strange indeed if the people’s lawyer were so perfectly insulated from any political—that is, popular—influence as Mr. Jaffer’s theory seems to hold. The only way the attorney general can reasonably be presented as the people’s lawyer is if he is selected by, subordinate to, and answerable to, someone who is himself the people’s elected servant. That person, again, is the president of the United States.

Those pressing these strange arguments—about the nature of an executive officer’s duty, and about the relationship of the attorney general to the president—have been educated at some of the nation’s most prestigious institutions and all now occupy positions of considerable public responsibility and influence. They either misunderstand the basic structures of American constitutionalism, or they are willing to misrepresent the Constitution in order to defend policy choices that they approve on other grounds. Both explanations are possible, and both are disturbing. The maintenance of free and responsible government depends upon the people’s accurate understanding of the nature and extent of the government’s powers. Such popular understanding is impossible to sustain, however, when the nation’s leadership class fosters, whether intentionally or unintentionally, public belief in fictional constitutional principles.