A New York federal judge signed off on Boston-based Am Law 200 firm Brown Rudnick's move to settle a $300 million malpractice suit dating to 2019 on Tuesday, just one day after the lawyer accused of a costly tactical blunder in a corporate bankruptcy announced his retirement.

The litigation trust established in the 2009 bankruptcy of chemical giant LyondellBasell had blamed the firm and attorney Edward Weisfelner for failing to demonstrate that a subsidiary was insolvent when it paid back $300 million in credit to billionaire Leonard Blavatnik, just months before the Chapter 11 filing. While the firm represented the trust in a 2016 trial against Blavatnik, it fell short in its bid to recoup the $300 million, winding up with only $12 million in breach of contract damages.