For starters, he recommended negotiating with their unions.

It may be sheer coincidence, but New Jersey seems have taken Judge Klein’s instructions to heart, even though states cannot file for bankruptcy and thus lack that particular leverage. For months, a pension commission formed by Governor Christie has been working quietly with the New Jersey Education Association, normally one of the state’s most litigious pension adversaries. By talking to each other instead of battling in court again, the two groups managed to find enough common ground to issue what they called a “road map” toward solving New Jersey’s daunting pension problems.

Many details remain in flux, and the union took pains on Tuesday to say it was not endorsing Mr. Christie’s full proposal and might never do so. But the road map identifies certain issues that are so important to New Jersey’s teachers that the union is willing to consider a pension freeze if that is what it takes to fully protect its members from the state’s looming pension collapse.

To appreciate how unusual it is for a state to propose a pension freeze, it helps to understand the “vested rights doctrine,” the legal argument that public pension plans cannot be frozen or reduced. Most states uphold some form of this doctrine, though in some it is a matter of statute, in others it is enshrined in the constitution and in still others it stems from court precedent. Often, the provisions have been in place for decades and attracted little notice until recently, when baby boomers began to retire in large numbers, placing unexpected pressure on public pension funds and the state and local budgets that support them.

People have sometimes suggested freezing public pension plans to keep the hole from getting deeper. But officials usually say that is impossible, and few want to mount a costly test of the doctrine, especially because the judges who would decide such a case usually participate in public pension systems themselves.

Companies, by contrast, can legally freeze their pension plans and have been doing so for years. Since 1974, companies with pension plans have been governed by a single federal law, the Employee Retirement Income Security Act, or Erisa, which details how freezes must take place to pass legal muster. One basic requirement is that workers midway through their careers are entitled to keep whatever portion of a pension they managed to earn until the date of the freeze.