Controversial US think tank the Heartland Institute has sent legal letters to bloggers and writers who reported on the release of the leaked Heartland Institute documents last week.

The Heartland documents revealed the key donors for the institute, plans for a K-12 curriculum based on a climate science denier agenda and how much well-known climate science denialists are paid to push the anti-climate change agenda for Heartland.

Heartland questioned the authenticity of some of the documents and threatened legal action last week. It proved over the weekend that it was going through with it, with a number of environment writers receiving legal letters.

“We realize this will be portrayed by some as a heavy-handed threat to free speech,” announced Heartland president Joseph L Bast in a press release. “But the First Amendment doesn’t protect Internet fraud, and there is no right to defamatory speech.”

Heartland’s communications spokesperson Jim Lakely told Crikey that so far five media organisations have been sent legal letters: Brendan de Melle from DeSmog Blog, Brad Johnson from ThinkProgress, Arianna Huffington from The Huffington Post, John H. Harris from Politico and Greg Laden, a blogger at ScienceBlogs. However at least one other climate blog received a legal notice notice.

Heartland has republished the letter it emailed to climate news website DeSmogBlog. The legal letter, written by Heartland’s general counsel Maureen Martin states:

“On or about February 14, 2012, your web site posted a document entitled ‘Confidential Memo: 2012 Heartland Climate Strategy’ (the ‘Fake Memo’), which is fabricated and false.

“On or about the same date, your web site posted certain other documents purporting to be those of The Heartland Institute (‘Heartland’). Heartland has not authenticated these documents (the ‘Alleged Heartland Documents’).

“Your site thereafter has reported repeatedly on all of these documents.”

It notes that Heartland is still investigating whether the leaked Heartland documents — excluding what they allege to be a fake climate strategy memo — “are authentic or have been altered or fabricated”, although they have been released publicly for five days already:

 “Though third parties purport to have authenticated them, no one — other than Heartland — has the ability to do so. Several of the documents say on their face that they are confidential documents and all of them were taken from Heartland by improper and fraudulent means. Publication of any and all confidential or altered documents is improper and unlawful.”

DeSmogBlog, which first published the leaked Heartlands document dump last week, is refusing to remove any of the documents or articles in question and said it will keep them in place as a matter of public interest.

“After due consideration, we could see no basis in fact or law for Heartland’s demand that we remove these documents,” wrote DeSmogBlog founding editor and well-known environment journalist Richard Littlemore.

Crikey spoke to the Vancouver-based Littlemore this morning. The legal letter is full of “logical inconsistencies at the very least”, Littlemore told Crikey.

“What they are saying is that we’re accusing you of theft but we can’t be sure that the stuff you have is stolen,” said Littlemore. “If the stuff is legitimate, then you can accuse someone of having stolen it. But if you can’t even satisfy yourself that the material is yours, then you’re certainly not in a very good position to tell anyone that they’ve stolen it.”

DeSmogBlog were sent the leaked documents after an individual pretended to work at Heartland and convinced the Institute to email them the allegedly confidential documents in full.

“If any of this turns out to be demonstrably incorrect then we will take that very seriously,” Littlemore told Crikey. “But in the meantime we look forward to reading and writing about the material.”

Greg Laden, a climate blogger at ScienceBlogs who also received the legal letter threat, agrees that the legal letter was confusing. Laden thought at first that the legal letter “looked like something some crazy denialist made up and sent me” since the  letter he received via email didn’t include his name in full (it’s Gregory), the title was wrong (he’s a doctor) and the address was wrong (he doesn’t live at the address or know anyone who does).

“As far as I can tell looking at it, no one I know who is a lawyer would retain staff who are as incompetent as those who wrote this letter,” said Laden.

How can Heartland seek action against a document it says is a fake? “They can’t take down a document they have nothing to do with,” said Laden. “If it’s made up and has nothing to do with Heartland, it would be difficult for them to argue that I should take it down off my website.”

But he sees the legal letter as a threat from Heartland against those who write about climate change and climate science. “It’s obvious to me Heartland is interested in making people who argue against their point of view quiet,” said Larden. “They want people to shut up.”

Crikey understands The New York Times will tomorrow reveal the identity of Heartland’s “Anonymous Donor”, an individual who has donated $13.7 million to the Heartland Institute since 2007 and at times has provided 60% of the institute’s funding.

Crikey asked Heartland to clarify how long it will take for all of the leaked documents to be authenticated, but we didn’t hear back before deadline.