Sullivan Mahoney LLP St. Catharines and Niagara Falls law firm. Niagara, Canada full service law firm. Sullivan Mahoney LLP prides itself on its tradition and integrity, and ability to adapt and adopt new technology and practices. Highly knowledgeable, skilled and experienced lawyers provide the highest level of service, and commitment to clients. Sullivan Mahoney LLP consists of several practice groups to better serve clients through specialized knowledge. The Niagara Region Law firm is also committed to St. Catharines and Niagara Falls communities through charitable donations, volunteering, fundraising and giving.