The term “fishing expedition” seems best suited to the high seas, or perhaps to the fertile waters off the Gulf Coast.

It’s hard to imagine a productive fishing expedition on Lake Contrary or most anywhere else in these parts. A fishing outing or day trip, perhaps, but not an expedition.

So how is it that we’re debating “expeditions” in Northwest Missouri? Leave it to the legal staff at Great Plains Energy Inc., which hopes to fend off irrelevant questions at regulatory hearings that might delay or derail its pending purchase of Aquila Inc.

Great Plains came up short last week in its bid to declare off-limits any discussion of the cost and other issues involving the new Iatan 2 coal-fired power plant under construction near Weston.

The Missouri Public Service Commission said it would allow “relevant” questions and evidence pertaining to such things as how the rising cost of the power plant could affect the debt rating for Great Plains, the parent company of Kansas City Power & Light.

The commission will allow subpoenas and depositions of current and former Great Plains and KCP&L employees. But it said the freedom to seek information that might show the purchase would be detrimental to consumers was not unlimited.

“The Commission is not … granting a blank check to any party to harass another party with discovery, or to attempt to burden the record in this case with irrelevant information or issues,” its ruling said.

This is as it should be. Provided the commission keeps the focus on relevant information, we find it hard to imagine this is not the right decision.

And we’ll add this caveat: When in doubt, prudence suggests regulators should err on the side of allowing testimony that is accurate and possibly relevant to deciding whether the Aquila purchase is good for consumers.

Heaven knows — and so do the customers of the former St. Joseph Light & Power — regulators need to get this decision right.