Voiding the mandate, or the entire law, would upend plans by insurers, employers

Popular provisions that have already gone into effect, such as letting children stay on their parents' insurance plans until they turn 26, would fall if the law is thrown out. If only the mandate is declared unconstitutional, however, the law would still affect millions.

The Wall Street Journal: Health Case Ripples Outward
Among those set to implement the law, insurers would have to ditch changes to their businesses designed to bring in millions of new customers. Provisions that have already gone into effect, including letting children stay on their parents' insurance plans until they turn 26, would no longer be required. Companies facing the law's requirements would be reprieved, including health firms set to pay new taxes and businesses that would have been required to insure their employees or pay a fee. It is impossible to predict how the court will rule, but skepticism from key justices heightened the possibility the 2010 health overhaul could be overturned in June, when the court is set to announce its opinion (Adamy, Bravin and Mathews, 3/28).

Kaiser Health News: Minus A Mandate, Health Law Would Still Affect Millions
If the Supreme Court strikes down the requirement that most Americans carry health insurance – along with related provisions that insurers must sell to people with pre-existing conditions and not charge the sick more – what's left in the law? Quite a bit, say policy experts – although the changes could make what's left harder to do (Appleby, 3/28).

The Connecticut Mirror: Supreme Court Sharply Divided Over Individual Mandate
At the center of the health care bill, the individual mandate helped persuade health insurers, including Connecticut-based companies like Aetna and Cigna, to accept other reforms on the way they do business. ... "Eight states enacted various (reforms) in the 1990s without covering everyone, and these reforms resulted in a rise in insurance premiums, a reduction of individual insurance enrollment and no significant decrease in the number of uninsured," AHIP President Karen Ignagni said (Radelat and Levin Becker, 3/27).