Bob McDonnell can breathe a sigh of relief, even if the Supreme Court only “springs” him in a theoretical sense. Out on bail while appealing his corruption convictions, McDonnell now has a clean record after having his case vacated this morning. He’s not out of the woods yet, though:

The U.S. Supreme Court on Monday threw out Republican former Virginia Governor Robert McDonnell’s corruption convictions in a ruling that could hem in federal prosecutors as they go after bribery charges against other politicians.

The court ruled 8-0 in overturning McDonnell’s conviction for accepting $177,000 in luxury gifts and sweetheart loans for him and his wife from a wealthy Richmond businessman seeking to promote a dietary supplement. The court found that McDonnell’s conduct did not constitute a criminal act under federal bribery law. …

The issue before the court was whether the gifts and money were part of an unlawful arrangement in which a sitting governor, in return for accepting them, employed the power of his office to benefit businessman Jonnie Williams.

The court ruled that the prosecution’s broad interpretation of the bribery law made it unclear whether McDonnell was convicted of conduct that was actually illegal. The court sent the case back to lower courts to determine if there is sufficient evidence for a jury to convict McDonnell. He could still face a new trial.

McDonnell didn’t win all of his arguments, but he won enough of them. The unanimous decision rejects his claim that the federal statutes in question are unconstitutionally vague, which would have precluded a retrial. They also rejected McDonnell’s argument that there wasn’t enough evidence that he committed an “official act” in exchange for remuneration, but that is less of a conclusion than a consequence of the overall decision.

The problem in the government’s case rests on their attempt to use an overinclusive definition of “official act,” and confusing the jury on that legal point. Chief Justice John Roberts makes the point in the summary:

(3) The question remains whether merely setting up a meeting, hosting an event, or calling another official qualifies as a decision or action on any of those three questions or matters. It is apparent from United States v. Sun-Diamond Growers of Cal., 526 U. S. 398, that the answer is no. Something more is required: §201(a)(3) specifies that the public official must make a decision or take an action on the question or matter, or agree to do so.

For example, a decision or action to initiate a research study would qualify as an “official act.” A public official may also make a decision or take an action by using his official position to exert pressure on another official to perform an “official act,” or by using his official position to provide advice to another official, knowing or intending that such advice will form the basis for an “official act” by another official. A public official is not required to actually make a decision or take an action on a “question, matter, cause, suit, proceeding or controversy”; it is enough that he agree to do so. Setting up a meeting, hosting an event, or calling an official (or agreeing to do so) merely to talk about a research study or to gather additional information, however, does not qualify as a decision or action on the pending question of whether to initiate the study. Pp. 18–22.

(c) The Government’s expansive interpretation of “official act” would raise significant constitutional concerns. Conscientious public officials arrange meetings for constituents, contact other officials on their behalf, and include them in events all the time. Representative government assumes that public officials will hear from their constituents and act appropriately on their concerns. The Government’s position could cast a pall of potential prosecution over these relationships. This concern is substantial, as recognized by White House counsel from every administration from that of President Reagan to President Obama, as well as two bipartisan groups of former state attorneys general. The Government’s interpretation also raises due process and federalism concerns. Pp. 22–24.

2. Given the Court’s interpretation of “official act,” the District Court’s jury instructions were erroneous, and the jury may have convicted Governor McDonnell for conduct that is not unlawful. Because the errors in the jury instructions are not harmless beyond a reasonable doubt, the Court vacates Governor McDonnell’s convictions. Pp. 24–28.

Roberts stresses in the opinion that the court takes no position on the ethics of McDonnell’s actions, and even refrains from providing a final judgment on whether these do qualify as “official acts”:

There is no doubt that this case is distasteful; it may be worse than that. But our concern is not with tawdry tales of Ferraris, Rolexes, and ball gowns. It is instead with the broader legal implications of the Government’s boundless interpretation of the federal bribery statute. A more limited interpretation of the term “official act” leaves ample room for prosecuting corruption, while comporting with the text of the statute and the precedent of this Court.

Nevertheless, this will make it more difficult to convict McDonnell in a future trial, and with him other public officials as well. The court insists on having a quid for the pro quo, and meetings aren’t enough to qualify. That certainly is enough to call McDonnell’s ethics into question, but that’s a political judgment, not criminal. Unless the government can prove that McDonnell took actions for a direct benefit — and real actions using the powers of his office, not just arranging meetings — it might be tough to get a jury to convict.

Chris Cillizza wonders if the Supreme Court has made corruption impossible to prosecute:

The court’s ruling (and its unanimous nature) affirms just how difficult it is to convict a politician of selling his or her office — unless that politician is either remarkably stupid or remarkably blatant in flouting the law. Unless you have somewhere in writing “Please give X person this official thing in exchange for a gift,” it’s very tough to prove that the reason a politician was motivated to help someone was because of a gift to them.

It’s why allegations of a politician voting a certain way in exchange for campaign contributions from an individual or group of allied interests almost never works. How can you disprove that the politician wasn’t acting in what he believed was the best interests of his state and not at the behest of campaign donors? You can’t — unless, as I noted above, the person is a giant moron and says that on tape or in writing.

That may be over-reading it. The opinion doesn’t really block juries from imputing motives — it just forces prosecutors to limit themselves to “official acts” that matter.

Besides, juries might be more inclined toward common sense even with a narrower definition of “official act.” Put a parade of “Ferraris, Rolexes, and ball gowns” in front of a panel of twelve citizens combined with the access that McDonnell’s friends got, and even a more limited instruction could well produce the same result. McDonnell might still have to find out.