Sally Yates, the former acting US attorney general, says she has deep confidence in special counsel Robert Mueller’s investigation into ties between president Donald Trump’s campaign and Russia. But she cautions that Mueller’s team has a narrow remit.

“Bob Mueller is going to be deciding whether or not crimes were committed, to be used for prosecution or impeachment,” Yates said onstage at the Aspen Ideas Festival today. “Surely that’s not our bar. That’s not the standard of conduct we’re looking for from our president or our administration. It shouldn’t just be whether you committed a felony or not. It should also be whether or not you’re observing the kind of norms that we’ve been talking about that are so essential to really the fabric of the rule of law.”

“There are facts here that should be alarming to us as a country that fall short of facts that establish a basis for impeachment or prosecution,” added Yates, a 27-year veteran of the Department of Justice who was fired by Trump for refusing to defend his travel ban, which she deemed unconstitutional.

Yates was echoing a view comprehensively expressed by David Frum in the Atlantic in May, before Mueller was appointed. Frum, arguing that what was needed was not a special prosecutor seeking crimes but an independent commission seeking truth, wrote:

A special prosecutor is uniquely poorly qualified to answer the single most important question about Trump-Russia: Why did Russia help Donald Trump? While it remains uncertain whether the Trump campaign colluded with Russia, it’s a fact accepted by everyone except Trump himself that Russia did intervene on his behalf. Why? This is an intelligence question with policy implications, not a prosecutorial question with legal implications. For example, if Russia preferred Trump because Putin liked Trump’s pro-Russia campaign policies—well, policies can be changed. But if Russia preferred Trump because Russian entities have some financial or other hold upon him—that’s something the country would need to know now, even if no crimes were involved.

Speaking in Aspen, Yates similarly argued: “So while I have total confidence in Bob Mueller and his ability to conduct this investigation, I don’t think that we should just be put all of our hopes into that will tell us whether anything bad happened here.”