The landmark Chevron decision concerning the scope of judicial review is under attack. For courts reviewing agency’s interpretation of a statute it administers the Supreme Court in 1984 established the principle that when the statute is ambiguous a court may not substitute its own opinion for a reasonable interpretation made by the agency. Chevron deference since then is a cornerstone of the American administrative state underlining the policy making capacity of agencies. But, today there are severe objections, not only but mostly by more conservative judges. Is an overruling of Chevron at stake?