The challenge in the coming months for Hawaii officials is how to make the square peg of the state’s longstanding health care statute fit into the round hole of the federal Affordable Care Act.

That story starts in 1974, the year that both the Employee Retirement Income Security Act (ERISA) passed in Congress and Hawaii enacted the Prepaid Health Care Act, which imposed an employer mandate to provide health coverage for employees working at least 20 hours a week. It also set a relatively high bar for what approved health plans must cover.

Here’s the rub: A section of ERISA voids state laws related to employer-sponsored health plans. Soon the Hawaii state law was challenged and in 1976 the U.S. Supreme Court struck it down.

It was salvaged by Hawaii’s congressional delegation, which got an exemption passed enabling Hawaii to be the only state with an employer mandate for health insurance. But the price of that survival is that the state has only limited power to change it.

Now the state’s free pass is about to expire. A state panel called the Prepaid Health Care Advisory Council will need to figure out how to marry the state law with the ACA, which pre-empts any provision of a state law that interferes with it. Health plans offered within the state are still subject to the Prepaid Health Care Act, but there are sizeable knots to untangle, said Ellen Carson, an attorney whose clients run the gamut of the isle health care industry.

Among the myriad questions to be settled: The state insurance exchange is supposed to offer patients more choice, with a range of price points based in part on what the consumer pays. Can the state law be stretched to enable that kind of flexibility?

Or, there’s the type of person to be covered, Carson said: The ACA’s employer mandates for coverage generally apply to those who work 30 or more hours per week, compared to the state’s 20-hour rule. Which hourly minimum will prevail?

Or, there’s the content of the plans. The state law requires coverage of a single in-vitro fertilization procedure in its plans.

"Will national plans coming into the exchange have to provide that?" Carson asked rhetorically. "There’s going to be some uneven competition going on."

Reconciling all of this is less a problem for the Legislature than the executive branch, said Beth Giesting, the state’s health care transformation coordinator in the Office of the Governor.

"The administration needs to be working as fast and efficiently as it can to get everything in line by the 2014 deadline," Giesting said.