* Guttenberg resigned in 2011 due to plagiarism charges
* Meeting with Merkel fuels speculation of comeback
* Op-Eds criticising Berlin policies spark backlash
BERLIN, Nov 29 (Reuters) - No German politician of the post-war era has had such a meteoric rise, and precipitous fall from grace, as Karl-Theodor zu Guttenberg, the Bavarian baron who fled Berlin for New York in 2011, his career in tatters over accusations of plagiarism.
At his peak in 2009, when he served as economy and then defence minister, Guttenberg was seen as a potential successor to Chancellor Angela Merkel.
His youthful charisma and readiness to speak out on controversial issues, from the war in Afghanistan to the rescue of carmaker Opel, made him the darling of a German media fed up with Merkel's colourless caution.
Germany had never seen a politician like him. A descendant of Leopold II, Holy Roman Emperor in the late 18th century, Guttenberg attended AC/DC concerts at night, had a glamorous wife, and could point to a family of Nazi resisters -- his grandfather is said to have narrowly escaped execution after saying that he'd rather kill SS officers than Jews.
When Guttenberg stepped down in March 2011 amid evidence he had copied large sections of his doctoral thesis, his exit was greeted with dismay, even by members of the leftist opposition. Merkel accepted his resignation with a "heavy heart".
Since leaving Germany two years ago, Guttenberg has lived with his wife Stephanie -- a great-great grand daughter of the first German Chancellor Otto von Bismarck -- and two daughters in the wealthy New York suburb of Greenwich, Connecticut.
He is a non-resident "distinguished statesman" at the Center for Strategic and International Studies (CSIS) in Washington and serves as ambassador for a European Commission initiative to promote internet freedom.
But until recently, he had kept a relatively low profile in Germany, returning home "rather frequently but very silently", he told Reuters in a recent telephone interview.
That changed earlier this month when Merkel received him in the Chancellery for a one hour "secret" meeting that was leaked to the media. What the two discussed remains a mystery, but the encounter was seen by some as a test of the public mood for a Guttenberg comeback.
Guttenberg declined to talk about the Merkel meeting and dismissed speculation of a return.
"I'm very happy over here," he told Reuters. "I'm finally diving into topics where a politician always pretends to have knowledge but usually doesn't have any."
"WAKE UP CALL"
If he is thinking of returning, Guttenberg is going about it in an interesting way. In a series of Op-Eds over the past year, he has openly criticised Merkel and her government on a range of foreign and security policy issues.
In late 2012 he took Berlin to task in the Financial Times for blocking the merger of Franco-German aerospace and defence group EADS and Britain's BAE Systems, calling the failed deal a "missed opportunity of historic proportions".
Last August, in the wake of a chemical weapons attack in Syria, he penned a piece in the New York Times denouncing Germany's "culture of reluctance" on military engagements.
His message -- that Germany should assume more responsibility in international affairs -- is not one that Germans are used to hearing from politicians at home, and the article sparked a fierce backlash in the national media.
"It was meant to be a wake up call," said Guttenberg.
He says his time in the United States has given him new perspective on Germany and its "inward looking" politics.
"The big difference I've sensed from over here is that expectations (of Germany) are actually much higher than is accepted in Berlin -- on foreign and security policy but also economically."
Guttenberg isn't shy about criticising German politicians on domestic matters either. In the interview, he faulted his own party, the Bavarian Christian Social Union (CSU), for its populist call, during recent coalition talks with Merkel, for national referendums on major EU decisions.
"I wonder whether it's the right signal," he said.
It was this kind of straight-talk -- in a consensus-driven country that has often seemed to eshew open political debate under Merkel -- that made Guttenberg, at his peak, one of Germany's most popular politicians.
Can he rehabilitate himself?
One problem is that Guttenberg has never really accepted the plagiarism charge, even after the University of Bayreuth, which awarded him a Ph.D. in 2006, ruled he had "extensively violated academic standards and intentionally cheated."
In Germany, politicians are expected to be above reproach and Guttenberg would have a tough time winning back the support of a German media that feels burned and betrayed by the man they made a star.
But time has a way of healing old wounds, and Guttenberg is only 41 years old.
A year ago, CSU leader Horst Seehofer, promised to bring him back to Germany after the Sept. 2013 federal election.
The natural place for him to relaunch his career, would be Bavaria, where his family traces its roots back to the 12th century and still lives in a castle it has owned since 1482.
"He can't return now -- the memory of the mother of all plagiarisms is still too sharp in people's minds," said Juergen Falter, a political scientist at Mainz University.
"But could it happen in a few years from now? Sure, it's possible. Guttenberg is still very popular, even among some Social Democrats. You have to go back to a young Helmut Schmidt to find a German politician with his charisma."
(editing by Janet McBride)