Nippon Steel and U.S. Steel sued the U.S. government Monday for blocking the merger of the two companies on national security grounds.

The suit, filed in the U.S. Court of Appeals for the District of Columbia Circuit, challenges the decision by President Joe Biden to reject the deal, arguing that the companies were denied due process and other rights and claiming that the $14.9 billion transaction was blocked for political reasons.

Determinations by the Committee on Foreign Investment in the United States (CFIUS) and subsequent national security decisions by presidents based on those determinations are generally not subject to judicial review, but some success has been achieved with claims involving questions about due process and procedural matters.