 Castor was defeated for re-election as Montgomery County's District Attorney in November 2015.Castor is a partner in the law firm of Rogers Castor and completed a nearly three year term as a special assistant district attorney of Centre County, Pennsylvania on December 31, 2017, followed by an appointment as a special assistant district attorney of Susquehanna County, Pennsylvania on January 6, 2018.On March 29, 2016, Pennsylvania Attorney General Kathleen Kane announced Castor's appointment (back-dated to March 21, when he actually took office) to the newly-created position of Solicitor General of Pennsylvania.