Williamson and Hayashi, LLC, is  committed to providing you with professional, experienced, and  personalized legal service for your municipal law needs.  Dave and Bill are graduates of the University of Colorado School of Law.   Our team understands the multiple facets involved in municipal law  matters and uses each of our relative experiences and areas of expertise  to efficiently meet your needs.  


David ("Dave") S. Williamson, Attorney

Dave earned his J.D. from the University of Colorado School of Law in 1977.  Dave also has a bachelor of science from the University of Colorado Business College in Finance (Cum Laude), which he received in 1974. Dave has been involved in municipal law practice since 1986, with experience as a deputy county attorney for Loudoun County, Va.; deputy city attorney for Thornton, Co.; and as an associate attorney at Windholz & Associates.  He was part of the Windholz & Associates team from February 1990 through February 2008, at which time Williamson and Hayashi, LLC, was formed.  Dave is presently the City Attorney for the City of Golden.  Other current and recent clients include:  City of Lafayette, City of Sheridan; City of Federal Heights; City of Edgewater; Estes Park Urban Renewal Authority; City of Longmont (Board of Adjustment); City of Walsenburg (Annexation, Land Use and Special District Matters); City of Westminster (Special Permit and License Board, and Sales and Use Tax Matters); and City of Thornton (Local Licensing Authority and Sales Tax matters).

William ("Bill") P. Hayashi, Attorney

Bill earned his J.D. from the University of Colorado School of Law in 1987, after receiving a Masters in Public Administration (1981) from the University of Colorado and a Bachelor of Arts, History from Denison University in Granville, Ohio. (1977).  Bill began his law career in the municipal law practice area, first as a law clerk for the City of Broomfield, then as an associate attorney at Windholz & Associates from December 1987 and February 2008, when Bill joined Dave Williamson in forming Williamson and Hayashi, LLC.  Bill is presently the City Attorney for the cities of Federal Heights and Sheridan and town attorney for Town of Firestone.  Other current and past clients include:  Assistant City Attorney for the Cities of Golden and Lafayette; Edgewater; Special Counsel for Estes Park Urban Renewal Authority; Municipal Prosecutor for the Cities of Broomfield, Edgewater, and Golden; Special Counsel to Commerce City (Personnel); Federal Heights (Codification); Westminster (Prosecutor); Broomfield (Liquor Prosecution); Federal Heights (Prosecutor); and Longmont (Board of Adjustment).

Keith Martin 

Keith earned his J.D. from DePaul University in 2009, after receiving a Bachelor of Science in Forestry from Colorado State University in 2004.  Prior to joining Williamson and Hayashi, LLC, Keith worked as an associate attorney at Hoffmann, Parker, Wilson & Carberry, P.C., where he served as a municipal prosecutor to several home rule and statutory towns and cities, represented clients in eminent domain and sales and use tax litigation, and advised clients on various legal issues related to tort liability, governmental immunity, open meetings, open records, employment, land use, legislative amendments, law enforcement, tax, and nuisance abatement.   He began his legal career in 2009 working as a law clerk for the City of Chicago in the Drug and Gang House Enforcement Section, eventually becoming an Assistant Corporation Counsel for the City of Chicago in 2011.  As an Assistant Corporation Counsel, he handled various civil litigation matters before administrative, state and federal courts, including public nuisance enforcement actions, employee disciplinary suspension appeal hearings, police discharge proceedings, and complex federal civil rights cases brought under 42 U.S.C. §1983.  Keith is an avid mountain biker who loves spending time outdoors with his family, teaching them about all Colorado has to offer and the importance of environmental sustainability.  

Mary Lynn Macsalka

Mary Lynn earned her J.D. from the University of Colorado Law School in 2008, and her Bachelor of Arts in Political Science from the University of Colorado, Boulder, in 2001 as a member of the President’s Leadership Class. She is a Colorado native and an experienced public sector attorney, having worked her entire legal career representing state and local government clients.   During law school, Mary Lynn clerked for Windholz & Associates, where she discovered her love for municipal law. Upon admittance to the Colorado Bar in 2008, she joined Williamson & Hayashi, LLC, where her practice focused on sales and use tax litigation, appellate practice, land use and development, zoning, nuisance enforcement, public contracts, liquor licensing and prosecution, legislation and ordinance drafting, open meetings, open records, and counseling local government clients on myriad legal issues.  In 2014, Mary Lynn moved to Anchorage, Alaska, where she worked as an Assistant Attorney General for the State of Alaska. She represented state agencies, boards, and commissions in state trial and appellate courts, and advised clients on a wide variety of matters, including municipal law, trust land management, grant program administration, rural energy project financing, campaign finance regulation, open meetings, public records, regulations drafting, legislation, and more.   Mary Lynn returned to Williamson & Hayashi in June 2019.  As of January 1, 2020, Mary Lynn  is the City Attorney  (Interim) for the City of Lafayette.   In addition,  Mary Lynn thoroughly enjoys collaborating with local public servants on the wide variety of legal issues unique to local government. Outside of work, Mary Lynn likes to get outside with her husband and four children, sharing with them all of the reasons she loved growing up in Colorado