The U.S. Supreme Court today will consider how much of President Barack Obama's health-care law must be thrown out if the justices decide Congress can't require Americans to buy medical insurance.

The debate on so-called severability took on added significance after questions from justices yesterday indicated a majority might strike down the insurance requirement. Today's session will conclude three days of hearings, six hours in all, the longest in 44 years.

The impact of the coverage mandate on the rest of the law is among the most important issues for the health-insurance industry. If the court strikes down the requirement, insurers want the justices to toss out provisions that forbid them from refusing coverage or charging higher premiums to people with pre-existing conditions.