Gabriel's most notable cases included representing victims of domestic abuse, Holocaust survivors, and groups facing hate-motivated violence.

In 2017, he filed two lawsuits against the Trump Administration on behalf of young illegal immigrants, also known as Dreamers, who were protected by the Deferred Action for Childhood Arrivals (DACA) program.

[9] Prior to his election in 2018, Gabriel served as a board member of the Jewish Federation of Greater Los Angeles and the League of Conservation Voters.

He won reelection to his first full term in the November 2018 General Election against Justin Clark, winning with 70.3 percent of the vote.

During his first full term in the State Assembly, Gabriel authored nine bills that were signed into law by Governor Gavin Newsom, including legislation to expand legal services for low-income Californians in civil cases and to establish a Nonprofit Security Grant Program to improve the physical security of nonprofit organizations that are at high risk of violent attacks or hate crimes.

[13] In 2023, Gabriel authored the California Food Safety Act, a bipartisan measure to ban red dye no.