In 2016, California lawmakers removed local barriers to accessory dwelling unit (ADU) construction by passing Senate Bill 1069.

[2] In 2019, the law was updated with Assembly Bill 68 to allow up to 500 of the 1,200 square feet to be designated a "junior accessory dwelling unit"; some commentators said this amounted to de facto triplex zoning throughout the state.

After the Senate concurred with the Assembly's amendments 28-7 on August 30, SB 9 was signed into law by Governor Gavin Newsom in September 2021, and went into effect on January 1, 2022.

The law requires local governments to modify or eliminate objective development standards on a project-by-project basis if they would interfere with construction of am otherwise-eligible SB 9 project.

Finally, the law requires the homeowner to sign an affidavit stating their intent to occupy one of the SB 9-applicable units as their primary residence for a minimum of three years.

[10] The author of the study recommended changes to the HOME Act, including more prescriptive land use and zoning standards, more flexible local SB 9 ordinances, and addressing homeownership barriers.

[21][22] After several charter cities sued in state court to block the enforcement of the HOME Act, on April 25, 2024, Los Angeles County Superior Court judge Chris Kin ruled against the constitutionality of the HOME Act in Redondo Beach, Whittier, Carson, Del Mar and Torrance, stating that the law did not specifically require property owners in charter cities to build below-market-rate, deed-restricted housing, and that the legislature had to demonstrate that the law addresses a statewide concern when applied to charter cities.