For years, Wisconsin courts gave “great weight” deference to agency interpretations of law under the following circumstances: 1) the agency was charged with the duty of administering the law in question by the legislature; 2) the agency’s interpretation is long-standing; 3) the agency employed its expertise or specialized knowledge in forming their interpretation; and 4) adopting the agency’s interpretation supports uniformity and consistency in the application of the statute. With those conditions being met, as long as the agency’s interpretation was “reasonable,” Wisconsin courts deferred to that interpretation.
However, that precedent has changed after Tetra Tech. “Great weight” deference is no longer a requirement and instead, Wisconsin courts will review agency interpretations of law de novo. The Supreme Court Justices were split on the rationale behind this decision and why they should do away with great weight deference and move to a de novo review of agency interpretations of law, but ultimately still came to the same conclusion that regardless of why, de novo review is the new standard.
“Due weight” deference was previously the “second” level of deference afforded agency interpretations of law in situations where the agency had some experience with the specific issue at hand but weren’t necessarily in a better position than the courts to come to a conclusion of law. It was referred to as the “tie goes to the agency” standard of deference. It appears that after Tetra Tech, “due weight” consideration will still be given to agency conclusions of law if the 4 factors noted above are met, but it will not be a matter of giving deference to the agency, the courts will simply look to the agency’s conclusion for persuasive value.