Applaud a group of retired state and federal judges from Pennsylvania who want Congress to open the curtain on secret campaign donors.

Judges, even when they're retired, rarely comment on public issues. But after watching the 2012 elections play out with hundreds of millions of dollars spent to secretly finance political ads, the judges decided to speak out.

They rightly argue that knowing who is behind a campaign ad gives voters more of a chance to evaluate that ad's credibility.

Elections are like trials, the judges say, with voters being the jury. Jurors must be able to evaluate a witness' motivation before deciding whether to believe his testimony. Without knowing who is sponsoring political advertisements, voters can't properly weigh an ad's arguments.

"To a judge, it's abhorrent to allow evidence in secret," says retired Lehigh County Common Pleas Court Judge Robert K. Young, who is heading the group. "If somebody tried to pull that off in our courtrooms, forget it. It's excluded." But political groups get away with it. They hide donors behind the tax code, which does not require "social welfare" organizations to disclose donors.

The government hasn't done much about it. With naive rulings, the Supreme Court opened the floodgates for secret money, but did not reject the need for disclosure. Congress, however, failed to use the window provided by the court to pass legislation requiring dark money to come into the light. Meanwhile, the Federal Election Commission is stuck in a partisan deadlock on the issue. And the Internal Revenue Service has yet to disclose the results of an investigation into whether any of these groups are violating tax law.

In the absence of federal help, a handful of states have made some progress unmasking secret donors. California and Idaho, in particular, have successfully used their state campaign finance laws to force disclosure.

New Jersey considered a law requiring the so-called social welfare groups to disclose donors if they spent money in state elections, but the bill died for lack of support. Pennsylvania, which doesn't even put a dollar limit on political contributions, has yet to consider a strong disclosure law.

The efforts in California and Idaho are encouraging, and helpful to citizens of those two more enlightened states. But even those measures don't address the overall problem of shadow groups. This is a national issue that should be dealt with at the federal level. The retired judges asked Congress to pass a disclosure law because it's Congress' role to turn the lights on those trying to secretly manipulate democracy.