On April 26, 2019 the US Court of Appeals for the District of Columbia Circuit struck down part of EPA’s TSCA Inventory Rule, which was adopted in August of 2017. The rule was an attempt to implement the 2016 TSCA statutory changes, which among other things, required EPA to update the TSCA Toxic Substances and Materials Inventory. Environmental organizations, including the Environmental Defense Fund (EDF), immediately challenged the rule on the basis that it failed to impose the proper standards for businesses to make confidentiality claims for chemicals required to be added to the inventory. In its decision, the court only struck down part of the rule for failing to include adequate substantiation questions regarding whether the identity of chemicals or substances for which a manufacturer or importer makes a confidentiality claim could be discovered via reverse engineering, as required by TSCA. Unless EPA chooses to challenge this decision to the US Supreme Court, it is now expected to correct the Inventory Rule consistent with this opinion.