The Franco-American patriarch of the Wildenstein art-dealing dynasty was on Thursday cleared by a Paris court of massive tax fraud.
The court said there was a "clear attempt" by Guy Wildenstein and seven co-defendants to conceal art treasures and properties worth hundreds of millions of euros from tax authorities.
But shortcomings in the investigation and in French legislation on tax fraud made it impossible to return a guilty verdict, presiding judge Olivier Geron said.
The "powerful and the poor" had equal right to justice, he said.
Wildenstein, 71, and other members of one of the biggest art-dealing families of the 20th century were accused of using a web of opaque trusts and tax havens to avoid paying tax on the bulk of a multi-billion-euro estate.
The allegations first surfaced over a decade ago when various Wildenstein widows and ex-wives, feeling shortchanged by the clan, began lifting the lid on their business dealings.
French tax authorities believe the Wildensteins owe them some 550 million euros.
After a month-long trial last year, prosecutors called for a two-year prison term for Guy Wildenstein and a fine of 250 million euros ($264 million) for what they called "the longest and most sophisticated" tax fraud scheme in modern-day France.
Wildenstein's nephew Alec Junior, his estranged Russian sister-in-law, Liouba Stoupakova, a notary, two lawyers and two offshore trusts were also tried over the alleged fraud.
The authorities alleged that on the death of their father Daniel in France in 2001, Guy and his brother Alec began hastily transferring assets abroad.
The brothers' stepmother Sylvia Roth later claimed she had been duped into relinquishing her share of the inheritance and successfully sued.
Guy and Alec Wildenstein together declared just 40.9 million euros for inheritance tax purposes in 2002. To pay the bill, they handed over bas-reliefs sculpted for Marie-Antoinette, the wife of Louis XVI.
Alec, who looked after the family racehorse business, is best remembered for his messy divorce from Jocelyn Perisse, a Swiss socialite hooked on facelifts who became known as the "Bride of Wildenstein".
Their divorce proceedings provided a first peek inside the business affairs of the secretive Wildensteins.
In 2008, after Alec's death, Guy Wildenstein declared an inheritance of $61 million -- an amount seen as conservative given the family's ownership of a trove of works by rococo painter Fragonard and post-impressionist Bonnard.
The estate also includes property, with the jewel in the crown being the game-filled Kenyan ranch that served as the backdrop for the film "Out of Africa".
The assets were mainly registered in tax havens in a series of trusts, one of which allegedly holds paintings worth an estimated one billion dollars.
During the trial Guy claimed he himself was mystified by the labyrinthine tax schemes put in place by his father and older brother Alec.
He has also argued that there was no legal obligation to report trust-held assets on his father's death.
The case has caused blushes for former French president Nicolas Sarkozy, who made Guy Wildenstein a commander of the Legion of Honour in 2009, one of France's highest honours. Sarkozy called Wildenstein a "friend".