As a member in the Maryland House of Delegates, Sossi was appointed to be the Deputy Minority Whip in 2007. He serves on the Environmental Matters Committee (2003–2011) and numerous subcommittees including local government & bi-county agencies subcommittee, 2003–05; housing & real property subcommittee, 2003–05, 2007-; natural resources subcommittee, 2003-; affordable housing work group, 2004; housing for individuals with disabilities work group, 2004; natural resources & ethics subcommittee, 2005; land use & ethics subcommittee, 2006; agriculture, agriculture preservation & open space subcommittee, (2006–2011); ground rent work group, (2006–2011); co-chair, abatement of drug-related nuisances work group, 2004); Chair, Queen Anne's County Delegation, (2003–2011). Member, Maryland Rural Caucus, (2003–2011); Maryland Legislative Sportsmen's Caucus, (2003–2011); Maryland Veterans Caucus, (2005–2011); Member, Bainbridge Development Advisory Board, (2003–2011); Task Force on Traffic Capacity Across the Chesapeake Bay, 2005–06; Task Force to Study Visual Smoke and Evacuation Alarms for the Deaf and Hard of Hearing, 2005–06; J. DeWeese Carter Center Advisory Board, (2005–2011); Task Force to Study the Boating Industry in Maryland, (2007–2011).