Health insurers in many states have been seeking double-digit premium increases from people who buy their own policies directly from the companies rather than obtaining group coverage at work. In states where regulators have the power to curb excessive rate hikes, the increases are often rejected or negotiated down. In those where the regulatory laws are weak not much can be done beyond jawboning.

This hodgepodge of controls over premiums needs to be backstopped by a national law that would allow the federal government to block unjustified rate increases where state officials lack the authority to do so. Attempts to include such powers in the newly enacted health care reform law failed. And while the reform law does have provisions that should help restrain premiums, they lack the necessary teeth.

The story of Anthem Blue Cross’s effort to impose big premium hikes on people who buy their own policies in California, a state with weak regulations, shows why that is so necessary. It also shows how difficult it is to measure what’s reasonable and how a confusing mélange of factors can affect the setting of premiums.

Anthem outraged its enrollees and much of the public in February with a plan to raise premiums for individuals by an average of 25 percent. The company argued that it lost money on the individual market in California last year, that medical costs were escalating far faster than inflation, and that the recession was causing relatively healthy individuals to drop coverage, driving up average costs for the remaining, less healthy enrollees.