HARI SREENIVASAN, PBS ANCHOR:

There was an important court ruling on Friday.

The Illinois Supreme Court voted unanimously to strike down a law passed in December of 2013 that was meant to rescue the state's pension system.

For more about the implications of that decision and what it could signal for other states, we are joined now from Chicago by Karen Pierog. She has been covering the story for Reuters.

So, bring us up to speed here. If somebody wasn't paying attention to what the law was in 2013, what did it try to do?