Photo of Juan A.  Marqués-Díaz

Juan A. Marqués-Díaz

Capital Member and Chair, Litigation Practice Group
787.250.2619 |


His practice includes general civil and commercial litigation before the Puerto Rico and federal courts, concentrating in local appellate practice, constitutional, tax, consumer class action, administrative, insurance - including healthcare insurance litigation - and land use litigation.

Mr. Marqués-Díaz has a solid constitutional law practice. He has argued many cases involving constitutional issues before appellate courts, including the first ever live TV broadcast oral argument before the Puerto Rico Supreme Court, which resulted in a unanimous landmark decision in favor of the firm's client. Brau et als. v. E.L.A. de Puerto Rico, 2014 TSPR 26 (2014).

Mr. Marqués-Díaz is ranked as one of Puerto Rico’s Leading Attorneys in the Dispute Resolution  field by the renowned international publication Chambers & Partners in its Latin America Guide. He is also ranked as a Leading Individual in Dispute Resolution by the Legal 500 ranking and in the Appellate Practice and the Arbitration and Mediation fields of The Best Lawyers in Puerto Rico guide. 

Prior to joining the firm, Mr. Marqués-Díaz clerked for the Hon. José A. Andréu García, Chief Justice of the Supreme Court of Puerto Rico, and also served as Special Aide to Chief Justice Andréu García. While in law school he served as Associate Editor of the University of Puerto Rico Law Review.

He frequently writes and lectures on alternative methods of dispute resolution. Also, he published “Notarización de Documentos de Extranjeros que no Entienden el Idioma Español o Inglés”  61 Rev., Jur. U.P.R. 193 (1992) and co-wrote “La Inconstitucionalidad de la Legislación de Antecedentes Penales de Puerto Rico” , 61 Rev. Jur. U.P.R. 115 (1992).

By appointment of the Puerto Rico Supreme Court, Mr. Marqués-Díaz has been a member of the Puerto Rico Board of Bar Examiners since 1997.

Representative Cases

  • Member of team that represented a major international retailer in a tax constitutional challenge before the federal court, on Commerce Clause, Equal Protection, and Federal Relations Act grounds. See Wal-Mart Puerto Rico, Inc. v. Juan C. Zaragoza-Gomez, 174 F. Supp. 3d 585 (DPR 2016).
  • Argued before the Puerto Rico Court of Appeals on several occasions, including on issues related to land use and constitutional topics such as whether there is a right to a jury trial in civil cases in Puerto Rico.
  • Represented the engineers’ professional liability insurer in the Superaqueduct complex construction litigation, which led to a landmark decision by the U.S. Court of Appeals for the First Circuit outlining the boundaries of mediation, and the eventual enactment of the local rule governing mediation in federal court. See In Re: Atlantic Pipe Corporation, 304 F. 3rd 135 (1st. Cir. 2002).
  • Defended taxpayers in tax deficiency proceedings brought by the Puerto Rico Treasury Department, the municipalities, and CRIM.
  • Represented petroleum companies in consumer class actions before the Puerto Rico and federal courts, and in multidistrict litigation before the U.S. District Court for the Southern District of New York.
  • Represented the PR Office of the Courts Administration in a case which resulted in the landmark decision in favor of client by the U.S. Court of Appeals for the First Circuit that Puerto Rico is not constitutionally required to provide a jury in civil cases. González-Oyarzun v. Caribbean City Builders, 798 F. 3rd 26 (1st Cir 2015).
  • His Puerto Rico Supreme Court published opinions include:
  • Lilly del Caribe, Inc. v. Municipio de Carolina, 2022 TSPR 101 (August 2, 2022); lead litigation counsel that successfully represented the taxpayer in a $14MM municipal license tax dispute on the scope of the exemption applicable to export sales made from a Foreign Trade Zone and the lack of authority of the municipality to impose requirements to claim an exemption in addition to those provided for in the statute.  
  • New Hampshire Ins. Co. y otros v. García Passalacqua y otros, 2021 TSPR 07; successful representation of the bond company in a case where the Supreme Court of Puerto Rico determined that the Puerto Rico Treasury Department did not have a preferential right, over the right of the bond company, to amounts deposited in Court by owners of projects for work done by a defaulted contractor who owed taxes and who had transferred all credits to the bond company.
  • McNeil Healthcare LLC v. Municipio de Las Piedras, 2021 TSPR 24; first Puerto Rico Supreme Court opinion on the certified public accountant privilege under Rule 504 of the Puerto Rico Rules of Evidence, extending privilege to communications among inhouse CPAs.
  • McNeil Healthcare LLC v. Municipio de Las Piedras, 2021 TSPR 33; opinion on whether the communications between experts and attorneys, and expert report drafts, are protected under the attorney/client privilege and work product doctrine.
  • Brau et als. V. E.L.A, 2014 TSPR 26 (2014), invalidating statute that modified retirement and other compensation rights of judges
  • Empresas Loyola v. Com. Ciudadanos, 186 D.P.R. 1033 (2012), reinstating construction permits for a residential development adjacent to an ecologically protected section of San Juan
  • San Antonio Maritime v. P.R. Cement Co., 153 D.P.R.374 (2001) acknowledging right of client to intervene in competitor’s administrative proceedings
  • Asociación Puertorriqueña de Importadores de Cerveza, Inc. v. Estado Libre Asociado, 171 D.P.R. 140 (2007) challenging preferential excise tax based on commerce clause considerations
  • Lilly del Caribe, Inc. v. Santos Rosado, 2012 TSPR 65 outlining requirements to challenge special tax
  • Pfizer Pharm. V. Mun. Vega Baja, 182 D.P.R. 267 (2011), where he appeared as amicus counsel for the Pharmaceutical Industry Association (establishing the limits of the municipality’s tax authority vis a vis tax exemptions granted by the Government of Puerto Rico)

  • His federal published opinions include:
  • Wal-Mart Puerto Rico, Inc. v. Zaragoza-Gómez, 174 F. Supp. 3rd 585 (2016), affirmed in 834 F. 3rd 110 (Ist Cir. 2016), invalidating a tax as unconstitutional on Commerce Clause, Equal Protection and Federal Relations Act grounds. 
  • González-Oyarzun v. Caribbean City Builders, 798 F. 3rd 26 (1st Cir 2015), holding that states are not constitutionally required to provide jury trial in civil cases.
  • Trilla-Piñero v. Puerto Rico, 557 F. Supp. 2d 258 (D.P.R. 2008) determining commencement of action under Class Action Fairness Act in gasoline industry litigation
  • Torres v. Bella Vista Hospital, Inc., 639 F. Supp 2d 188 (D.P.R. 2009) successful defense of ERISA claim
  • Milliman, Inc. v. Health Meadicare Ultra, Inc., 641 F. Supp. 2d 113 (D.P.R. 2009) compelling arbitration of contractual dispute


News & Publications


Member, Policy Committee

Leader, Alternative Dispute Resolution Practice Team

Co-Leader, Tax Litigation Practice Team

Bar Admissions


B.A., University of Notre Dame, 1988

J.D., Magna Cum Laude, University of Puerto Rico Law School, 1991

LL.M., Harvard Law School, 1994


Puerto Rico Bar Association

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