Illinois legislators can run, but they can't hide from the state's public pension woes.

Last year, Illinois legislators significantly changed the pension rules for public employees hired after Jan. 1, 2011.

This year, they're showing signs of tackling the dramatically more difficult issue of revising the rules for the older employees not affected by the rules for new hires. Whatever they do, it won't be easy.

There are both political and legal hurdles to passing revisions to pension rules that might include enhanced employee contributions or an older retirement age. But the chronic underfunding of the state's public employee pension programs and the state's massive budget deficits and overall debt – even in the face of recent income tax increases – require a serious effort be made to address the problem.

That's why Illinois House Speaker Michael Madigan has been talking about putting a bipartisan bill together, and that's why David Vaught, Gov. Pat Quinn's budget adviser, was quoted recently as saying that "there is growing momentum for additional pension reform." He went on to state that the issue is "something that definitely should be looked at."

Even more important than what Vaught said is what Gov. Quinn's budget proposal said and then tried to un-say.

Quinn's voluminous budget document stated that state pensions may need a "federal guarantee." Vaught later disclaimed the language, saying the controversial reference "should have been edited out" because "we don't think we need a bailout."

But it's impossible to un-ring a bell. That explosive reference to the necessity of a federal guarantee, which won't be coming, for Illinois' underfunded pension system didn't make it into the budget by accident. Obviously, the issue has been a subject of serious discussion, and that speaks volumes about the need for legislative action.

But pension reform will prove to be a sticky wicket for a variety of reasons.

For starters, the powerful public employees' unions hate the idea. They wield lots of clout, mostly in the form of campaign contributions and workers for favored politicians. The Democrats who control the Legislature are generally union-friendly. So this could be a fight within the family, and those are especially ugly.

Then there is the legal issue. There are serious questions about whether changes in pension rules are permitted under the Illinois Constitution.

Senate President John Cullerton has opined that it's impermissible to hire an employee under one set of rules and then change the rules, relying on a lengthy opinion prepared by one of his staff members.

However, last year the Civic Committee of the Commercial Club of Chicago solicited an opinion on the issue by the prestigious firm of Sidley Austin and received a different analysis. The Sidley Austin opinion held that benefits already earned cannot be reduced but future benefits can be modified.

Of course, what really matters is how the courts interpret the law, and that will require the Legislature to pass a bill that ultimately will be reviewed by the Illinois Supreme Court.

Unfortunately, Gov. Quinn has indicated he will not lead on this issue. Vaught said only that Quinn "would not stand in its way" if the Legislature tackles the problem.

Much as some legislators may hate the idea, they really have no choice but to move on this issue. Thanks to decades of neglect, Illinois has the most underfunded public pension systems in the country. This financial time bomb must be defused.