The Supreme Court nomination of Neil Gorsuch helped propel a largely academic debate over judicial deference to agency interpretations of law to the fore. Under the Chevron doctrine, agency interpretations of ambiguous statutory language are to be upheld, provided that the agency interpretations are themselves reasonable. Although Chevron deference is not always available, when it can be invoked it helps agencies defend their actions in federal court. Then-judge Gorsuch’s opinions questioning Chevron highlighted long-simmering disputes over the doctrine’s wisdom. (For my own take on this question, see here.)

In theory, Chevron helps prevent judges from relying upon their own policy preferences when reviewing agency decisions. It does this by instructing courts to defer to agency decisions about how ambiguous statutory language should be interpreted. In effect, it tells judges: Unless the statute is clear, let the agency have its way, provided it’s not doing anything the statute clearly prohibits.

Does Chevron fulfill its purposes? A new paper by Kent Barnett, Christina Boyd and Christopher Walker shows that appellate courts are not as consistent in applying Chevron deference as some might like. Here’s the abstract:

Do federal circuit courts consistently apply Chevron deference’s framework when reviewing agency statutory interpretations? Or do political dynamics result in courts gaming the Chevron doctrine? To answer these questions, we empirically analyze circuit-court decisions from 2003 until 2013 that review agency statutory interpretations. Our results — from the largest and most comprehensive database of its kind — confirm longstanding intuition and earlier, more limited studies: courts do not consistently apply Chevron. Our findings, nevertheless, offer some surprising insights into the political dynamics of applying Chevron. When courts reviewed liberal agency interpretations, all panels — liberal, moderate, and conservative — were equally likely to apply Chevron. But when reviewing conservative agency interpretations, liberal panels applied Chevron significantly less frequently than conservative panels. Contrary to limited prior studies, we find no evidence of “whistleblower” or disciplining effects when judges of different judicial ideologies comprised the panel. Viewed together, our results provide important implications for the current debate on whether to eliminate, narrow, or clarify Chevron’s domain.

Worth highlighting is the apparent finding that liberal and conservative panels are not equally consistent in their application of Chevron. As the authors discuss in the paper:

It turns out that conservative judges tend to apply Chevron deference at effectively the same rate regardless whether the agency interpretation is liberal or conservative. And liberal and conservative judges apply Chevron at effectively the same rate for liberal agency interpretations. But when it comes to conservative agency interpretations, we find that liberal judges are less likely to apply Chevron deference. In other words, Chevron deference appears to constrain conservative judges as to liberal interpretations, but not vice versa.

What does this mean? There are several possibilities. Among other things, it is possible that conservative agency interpretations are less likely to be worthy of Chevron deference, perhaps because existing regulatory statutes have underlying liberal purposes or Republican administrations are more prone to taking liberties with statutory language in agency implementation. (See, for instance, the George W. Bush administration’s approach to the 1990 Clean Air Act, which led to repeated losses in federal court.) Under this interpretation, liberal judges are simply more likely to call out such excesses than are conservative ones.

Another possibility, of course, is simply that liberal judges are less constrained by Chevron than their conservative brethren. Under this interpretation, suggested by the authors, such judges are less likely to grant Chevron deference to agency actions with which they disagree. This would suggest that Chevron does not consistently constrain judges from considering or relying upon their policy preferences in rendering their decisions. Without looking at the specifics of the agency actions under review, it is impossible to know for sure.

As the authors note, this research is of potential relevance to ongoing debates about whether Chevron deference is worthwhile. As a general matter, Chevron deference helps agency actions survive judicial review. As prior research has shown, agencies tend to win in appellate courts when Chevron deference is applied. Yet this new research suggests Chevron might not help all agency actions equally.

Some commentators have suggested that abandoning Chevron deference now might make Trump administration deregulatory efforts more vulnerable to judicial review. Yet if liberal judges are less likely to apply Chevron to conservative agency actions — such as efforts to deregulate — abandoning Chevron might not matter as much in a court such as the U.S. Court of Appeals for the D.C. Circuit, which has a sizable liberal majority. This could make the Trump administration more willing to support proposed legislation to eliminate Chevron deference. Such legislation has already passed the House and is under consideration in the Senate.