New York Attorney General Eric T. Schneiderman speaks at a March 29 news conference on a state-based effort to combat climate change. (Mike Segar/Reuters)

Sam Kazman is general counsel and Kent Lassman is president of the Competitive Enterprise Institute.

With seven state attorneys general and Al Gore sharing a New York City stage , there was no doubt about it: It was showtime for a whodunit. The crime being investigated? Dissent.

The March 29 news conference unveiled, according to New York Attorney General Eric T. Schneiderman, an “unprecedented” coalition to fight not only climate change but also allegedly deceptive speech about climate change. The group, which dubbed itself AGs United for Clean Power, promised to “use all the tools at our disposal” to battle for progress on “the most consequential issue of our time.”

Schneiderman was blunt about his goal of shutting down debate: “You have to tell the truth. You can’t make misrepresentations of the kinds we’ve seen here.”

This isn’t a law-and-order drama. It’s politics clothed in messianic garb, and its primary tools are censorship and intimidation.

The AGs are following a familiar script here: target an unpopular, deep-pocketed business, harass that business’s potential allies with overly broad investigations, run roughshod over the target’s First Amendment protections and settle once the politically weakened company tires of fighting the endless resources of the state.

ExxonMobil was singled out by name at the news conference, but the coalition appears to be following the script perfectly. Now it’s on to the fishing-expedition stage.

On April 7, our organization, the Competitive Enterprise Institute, was subpoenaed by coalition member and U.S. Virgin Islands Attorney General Claude Walker for all CEI material on climate change and energy policy, as well as information on our supporters, over 10 years beginning in 1997. The subpoena’s purported focus is on our contacts with ExxonMobil, a former CEI donor that publicly ended its support for us after 2005. Nonetheless, the subpoena calls for practically all of our material on climate change and energy policy, as well as information on any donors who directly or indirectly supported that work.

That’s one hell of a burden to slap on a nonprofit. The coalition’s purported justification is that the risks of global warming are so important and the scientific basis for them so settled that disputing them constitutes fraud. But the rhetoric of the AGs is blissfully oblivious to the First Amendment.

Court rulings make it clear that broad subpoenas aimed at restricting speech, especially in the context of policy debates, are invalid. Time and again, the Supreme Court has held that the remedy for unwanted speech is more speech in response. The chief law-enforcement officers of several states should know better, but their reaction to a dissenting policy position is punitive, coercive and unconstitutional.

As for breaching donor confidentiality, the obvious aims here are intimidation and to limit future use of the constitutionally protected right of anonymous donation. In 1958, in NAACP v. Patterson, the Supreme Court held that such attempts were illegal under the First Amendment’s right of association.

You might think that if the law is that clear, we have nothing to worry about. But fighting a subpoena is incredibly costly and time-consuming, especially when the attorneys general behind them have promised to “use all the tools” at their disposal, courtesy of their states’ taxpayers.

Regardless of where you stand on global warming policy, the notion of a multi-state campaign to end the debate ought to make you worry. After all, there are many science-driven policy debates out there, on topics ranging from genetically modified food to population control. It is not as if the government has a sterling reputation when it comes to science. From Galileo to today’s food plate, we know government politicizes science. It ought not to punish dissent, too.