Consumers and insurers face new uncertainty with the Justice Department’s assertion this week that key provisions of the Affordable Care Act are invalid.

In a brief filed Thursday, the department asked a federal court to unwind the health law’s protections for individuals with existing medical conditions, such as diabetes or asthma. The law, known as Obamacare, prohibits insurers from refusing to sell coverage to people with pre-existing conditions or from charging them more than healthy consumers.

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