Paul C. Castañeda has been an outspoken activist on labor, social, and economic justice. He was a founding member of Citizens for a Better Arizona and served on the Board of Directors as the Treasurer. Paul has been a union member of the Communications Workers of America Local 7019 for 21 years. He served as an Area Vice President, Vice President, Executive Vice President, and President of Local 7019 for 16 years.

During his time as a local officer, he was appointed to the CWA National Committee on Civil Rights and Equity. Paul also served as the Chair of the Maricopa Area Labor Federation for 5 years and on the Executive Council of the Arizona AFL-CIO for 6 years.

In 2015, Paul was promoted as a Staff Representative for the Communications Workers of America with responsibilities of supporting locals in Arizona, Utah & New Mexico in bargaining, grievance, and arbitration processes, steward training, and coordinating legislative and political issues.