The most important parts of the drone memo are the parts you can’t see.

The memo, released by a federal court on Monday in response to lawsuits filed by the ACLU and The New York Times, addresses the government’s authority to carry out “targeted killings” of American terrorism suspects. Written in the summer of 2010 by the Obama administration’s Office of Legal Counsel, the memo supplied the legal basis for the government’s premeditated killing of Anwar al-Awlaki, an American, in the fall of 2011.

The memo sets out a legal argument based on stipulated facts – that is, based on facts assumed to be true. Al-Awlaki was a leader of a group “in league with” Al-Qaida, the memo says. The group had a “significant and organized presence” in Yemen, from which it was planning attacks against the United States. Al-Awlaki himself presented a threat that was “continuing and imminent.” Killing him was feasible, but capturing him was not.

“The memo’s conclusions depend entirely on factual assumptions that are stated but never explained, let alone defended. The redacted memo is like a play in which the main characters never appear on stage.” Jameel Jaffer, deputy legal director at the ACLU

Once these facts are assumed, the memo’s ultimate conclusion – if not its legal analysis – follows inevitably. How could it not? No government would disclaim the authority to use force as a last resort against a serious threat that was truly imminent.

But even if we assume, against the evidence, that the memo is using words like “imminence” and “feasible” in conventional ways, what assurance do we have that the facts the memo accepts as true were actually true? What assurance do we have that Al-Awlaki was who the memo says he was, and that he was doing what the memo says he did?

The first 11 pages of the memo, in which the Justice Department’s factual assumptions are set out in detail, have been redacted – censored – on the grounds that their disclosure would compromise sources and methods. Many other sections of the memo have been redacted on the same grounds. The memo’s conclusions depend entirely on factual assumptions that are stated but never explained, let alone defended. The redacted memo is like a play in which the main characters never appear on stage.

The debate over the memo’s legal analysis is important, and those who are asking questions about the way the government has (or has not) defined key terms, and about the way it has described the scope of the armed conflict, are entirely right to do so. But even the most searching evaluation of the memo’s legal analysis won’t tell us whether the government’s killing of Anwar al-Awlaki was lawful. To answer that question, one needs access to the pages the government has redacted.

Even access to those pages would not be enough, because those pages include only the intelligence agencies’ allegations. The intelligence agencies have never been compelled to substantiate these allegations to anyone outside the executive branch, or submit them to cross-examination, or establish them beyond a reasonable doubt. The entire memo rests atop a foundation whose solidity we can’t know.

There is no justification for this secrecy. If the government had indicted al-Awlaki for a terrorism-related offense and prosecuted him in an ordinary federal court it would have had to present its evidence to a judge and jury. Defense counsel would have reviewed and challenged it. Members of the public would have been able to attend the proceedings, and journalists would have been able to report on them.

Something similar would have happened if the government had imprisoned Al-Awlaki as an enemy combatant. Al-Awlaki would have been entitled to a hearing before a federal judge, and there would have been a heavy presumption against secrecy. Publicity would have ensured a kind of accountability.

The government should not be able to avoid this kind of accountability simply because it killed al-Awlaki summarily rather than charged him with any offense. The government has an interest in protecting legitimate sources and methods, but Americans have an overriding interest in ensuring that the government’s use of lethal force is legitimate.

Now that the drone memo has been released, the government will have a difficult time explaining why other legal memos relating to the targeted-killing program should be withheld. One result of the ACLU and The New York Times lawsuit is that a federal judge will now review those still-withheld memos for possible release. But the disclosure of legal analysis alone is not enough – the public is entitled to the facts, too. When the government kills, it needs to explain why.

Jameel Jaffer is deputy legal director at the ACLU.