Professor Yen has published numerous articles about copyright law, the Internet, sports law, Asian-American legal issues, and law teaching. He is the co-author of the casebook, Copyright: Essential Cases and Materials, 3d Ed. (West Publishing, 2016). He has served as Chair of the AALS Professional Development Committee and completed a term on the Board of Editors for the Journal of Legal Education and the Board of Governors for the Society of American Law Teachers. Additionally, Professor Yen has served as chair of the Association of American Law Schools Section on Art Law and its Section on Minority Groups. He organized the first, fifth, and tenth Conference of Asian Pacific American Law Faculty.

In 1992, Professor Yen wrote and filed an amicus brief with the United States Supreme Court on behalf of 12 copyright scholars in the case of Campbell v. Acuff-Rose Music Publishing Co. He also joined another group of copyright scholars to file an amicus brief in the case of A&M Records. Inc. v. Napster, Inc. during the summer of 2000. In 2001, the American Law Institute elected him to membership in the Institute.   Before joining the faculty in 1987, he practiced law in Los Angeles for four years at the firm of Sheppard, Mullin, Richter and Hampton.