California v. Texas is a significant Supreme Court case decided in 2021 that challenged the constitutionality of the Affordable Care Act (ACA), particularly focusing on the individual mandate, which required individuals to purchase health insurance. This case arose when several states, led by Texas, argued that the mandate was unconstitutional after Congress reduced its penalty to $0 in 2017. The Supreme Court ultimately ruled that the plaintiffs did not have standing to sue, allowing the ACA to remain in effect and highlighting the ongoing debates over healthcare reform and state versus federal powers.