Disparate-impact theory is a legal doctrine under civil-rights statutes (including the Fair Housing Act) that treats a facially neutral policy as unlawful when it causes a significant disproportionate harm to a protected group. Courts and HUD typically apply a burden‑shifting test: a complainant must show a policy causes a discriminatory effect; the defendant can justify the policy by showing a legitimate, necessary reason (e.g., business or programmatic necessity); and the complainant can then show a less‑discriminatory alternative that achieves the same goal. The U.S. Supreme Court recognized disparate‑impact claims under the Fair Housing Act in Inclusive Communities (2015) but required plaintiffs to show a robust causal link and cautioned against using disparate impact to pursue minor or speculative disparities.