IMHO, it was when the court - reformed itself - under the threat of the court packing plan, and then the new deal legislation / regulation was approved by the court. But even the reformed court, several years latter, so the folly of the new deal price controls, and even that liberal court started stricking down some of the legislation, the sick chicken case, etc. And also the passage of the 17th amendment - direct election of the Senate - made the issues worse - and as an indirect results lead to the creation of the unfunded mandates from the feds (a massive power grab). Marbury was correctly decided.