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About me

Attorney Sean M. Sweeney is a partner with Halling & Cayo, S.C. and has the requisite skills, education, and experience to help serve all of your legal needs in the Wauwatosa and Milwaukee area.

Sean earned his Juris Doctor (JD) and Masters of Business Administration (MBA) from Marquette University. He earned his Bachelor of Science degree in Business Economics from Northern Arizona University.

Before opening his own practice, Sean worked for the Milwaukee Bucks as a legal intern drafting and reviewing big dollar sponsorship deals. Sean has experience drafting contracts ranging from small business contracts to plow a parking lot to large corporation contracts dealing with operating and maintaining real estate.

Sean has not only the legal training and experience needed to provide complete service, he also has the education and training to understand the real world needs and challenges that organizations large and small face today.


Guardian Ad Litem's Office: While in Law School Sean worked for the Guardian Ad Litem's Office in the Children's Court. While there, he worked on cases involving Children in Need of Protective Services actions as well as Termination of Parental Rights actions. Sean also researched extensively and helped prepare for a Wisconsin Supreme Court case involving a Termination of Parental Rights action.

Milwaukee and Waukesha County Public Defenders Appointments: Tosa Law Office has represented clients as a Public Defender appointed Attorney in both Milwaukee and Waukesha counties. The public defenders office provides legal assistance to those people charged with a crime who do not have the means to pay for counsel on their own. Often times the Public Defenders Office is not able to adequately serve all of the people who need assistance, therefore attorneys such as Sean with Tosa Law Office take some of the surplus cases to help ease the burden on the often overtaxed public defenders office.



Big Brothers Big Sisters: Sean has been a Big Brother through the Big Brothers Big Sisters organization in Milwaukee since July of 2007. Sean has been placed with a little brother, Sema-j, Sema-j and Sean have had a lot of fun together and the experience has shown to be very rewarding for both Sean and Sema-j. As a personal recommendation, I would ask that anyone who has the time, (just a few hours a month) should sign up to be a big brother or big sister. I do not know of any other way to more significantly impact a young persons life than to simply take an interest and help teach them how to feel good about themselves and be successful in life. This request comes doubly for Men to be big brothers as there is always a shortage of Big Brothers vs. Big Sisters.


Languages spoken: Spanish

Photos and videos

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Practice areas


  1. Litigation: 55%
  2. Business: 15%
  3. Investment Fraud: 15%
  4. LLC: 5%
  5. Other: 10%
  6. More 



Retainer (sometimes)

Payment types:

Cash, Check, Credit card

Attorney endorsements

27 total 

Are you an attorney? Endorse this lawyer

  • M. Todd Miller

    I endorse this lawyer.


    M. Miller Tax Attorney
    Relationship: Fellow lawyer in community

  • Joseph Cohen

    I've enjoyed getting to know Sean over the last few weeks. Not only is he an excellent attorney, but his experience running his own practice helps him serve his business litigation clients exceptionally well.


    Joseph Cohen Estate planning Attorney
    Relationship: Fellow lawyer in community

Contact info

Halling & Cayo SC

320 E. Buffalo St.
Suite 700
Milwaukee, WI, 53202-5837


WIGood Standing200703/26/2015
We have not found any instances of professional misconduct for this lawyer.
Avvo contributions
Legal answers
Award nameGrantorDate granted
Rising Star - LitigationSuper Lawyers2014
Leading Lawyers - LitigationM: Milwaukee's Lifestyle Magazine2014
Leading Lawyers - LitigationM: Milwaukee's Lifestyle Magazine2013
Rising Stars - Business LitigationSuper Lawyers2013
Up-and-Coming LawyerWisconsin Law Journal2013
Leading LawyersMilwaukee Lifestyle Magazine2012
Rising StarSuper Lawyers2012
Rising StarSuper Lawyers2011
Thomas Moore Law ScholarshipMarquette University Law School2004
Work experience
TitleCompany nameDuration
ShareholderHalling & Cayo, S.C.2013 - Present
AttorneyHalling & Cayo, S.C.2008 - 2013
AttorneyTosa Law Office2007 - 2008
Legal InternMilwaukee Bucks2006 - 2006
Association namePosition nameDuration
Public Investors Arbitration Bar AssociationPIABA Member2011 - Present
Milwaukee Bar AssociationN/A2007 - Present
State Bar of WisconsinN/A2007 - Present
State Bar of Wisconsin, Litigation SectionN/A2007 - Present
State Bar of Wisconsin, Business Law SectionN/A2007 - Present
Wisconsin Solo and Small ConferenceCo-Chair Technology Comittee2011 - 2012
Solo and Small Firm Conference Technology CommitteeMember2010 - 2012
National Sports Law InstituteN/A2004 - 2012
Legal cases
Case nameOutcome
Federal TILA Rescission and Fraud CasePending
Direct-TV Commercial License DisputeSettled
Joint Venture AgreementSuccessful Business Relationship
See all legal cases 
Publication nameTitleDate
Wisconsin Securities FraudPermanent All-Public FINRA Arbitration Program Could Pay Dividends for Investors2011
Milwaukee Business LawyerWhat lien rights do I have as a commercial sub-contractor2011
Wisconsin Securities FraudWhat is FINRA Arbitration2011
Milwaukee Business LawyerWhat do I do if I have been sued with a frivolous claim?2011
Milwaukee Business Lawyer BlogWhat Happens if I get sued?2010
Milwaukee Business Lawyer BlogCan I just close my doors if my business is sued?2010
Wisconsin LawyerHow can I avoid Problem Clients or ethically disengage from representing one?2008
Milwaukee Business Law BlogThe Anatomy of a Contract2008
Milwaukee Business Law BlogHow will the bailout effect businesses in Milwaukee2008
Milwaukee Business Law BlogThe Problem with On-Line Form Contracts2008
School nameMajorDegreeGraduated
Marquette UniversitySports BusinessMBA - Master of Business Administration2007
Marquette University Law SchoolLawJD - Juris Doctor2007
William & Mary Law SchoolStudy Abroad in Madrid, SpainN/A2006
Loyola Law School, Loyola Marymount UniversityStudy Abroad in San Juan, Costa RicaN/A2005
Northern Arizona UniversityBusiness EconomicsBS - Bachelor of Science2004
Towson UniversityBusiness EconomicsNational Student Exchange Program2003
Seton Hill CollegeEuropean Study AbroadN/A2000
Speaking engagements
Conference nameTitleDate
Business Law - WCTCContract Law Basics2014
Lorman CLELLCs From a Litigator's Prospective - Resolving Litigation2013
Lorman CLELLCs from a Litigator's Prospective - Avoiding Litigation2013
Wisconsin Bar Litigation ConferenceFINRA Mediation and Arbitration2012
Milwaukee Bar Association, PresentsInvestment Fraud, from Wall Street to Main Street2012
Wisconsin Solo and Small Firm ConferenceHidden Gems in Adobe2011
Wisconsin Solo and Small Firm ConferenceEthics of Social Media2010
Wisconsin Bar Leaders ConferenceUsing Blogging as an effective communication tool2009
Negotiating the Transition from Law School to PracticeSolo-practice management.2008