Question: What was the reason given for the confiscation of the artwork "Portrait of Dr. Gachet"?
About the article "Portrait of Dr. Gachet", section "Original version".

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The Gachet Family.
"Portrait of Dr. Gachet" is one of the most revered paintings by Dutch artist Vincent van Gogh of Dr. Paul Gachet, who took care of him in his last months.
In 1990, it fetched a record price of $82.5 million ($75 million, plus a 10 percent buyer's commission).
Gachet was also an artist of the Impressionist era.
He was an amateur painter and engraver.
Vincent van Gogh went to the doctor for medical care.
Van Gogh saw himself in the doctor; like himself, he saw in Dr. Gachet “the heart-broken expression of our time.” Similar to many of van Gogh’s portraits, the painting is a study not of the physical features of the man, but of the inner qualities of the doctor’s personality.
The portrait of Dr. Gachet notes all the tiniest details of his appearance and depicts them in the way that van Gogh sees them.
The characteristics of the doctor’s image are all freely painted so that the viewer may see them the same way that van Gogh does. 
Van Gogh, introduced to etching by Gachet, made the etching "Portrait of Doctor Gachet" in 1890.
Gachet and Van Gogh discussed creating a series of southern France themes but that never happened.
This was the one and only etching, also known as "L'homme à la pipe" (Man with a pipe), that Van Gogh ever made.
Van Gogh's brother, Theo, who received an impression of the etching, called it "a true painter's etching.
No refinement in the execution, but a drawing on metal."
It is a different pose than that in Van Gogh's "Portrait of Dr. Gachet", owned by Musée d'Orsay.
The National Gallery of Canada finds that "The undulating flow of the line is typical of the expressive quality of Van Gogh's late style."
The impression owned by the National Gallery is from one of the 60 printings following Van Gogh's death by Dr. Gachet's son, Paul Gachet Jr. Gachet's collector's stamp appears on the bottom edge of the print. 
Sue Roe, author of "The Private Lives of the Impressionists", wrote of Dr. Gachet's garden:"Dr. Gachet's house was set in the hillside above the main street the village, with a terraced garden full of flowers and looking down into the valley of the Oise.
The house and garden were always full of stray cats, chickens and a ragged, featherless rooster...
In the garden, he Gachet worked at a table painted bright orange (later immortalized by Van Gogh, in his Portrait of Dr Gachet)."
"Maison du Dr. Gachet," the house and gardens of Dr. Paul Gachet, was opened to the public in 2004. 
Gachet was friends with and treated Pissarro, Renoir, Manet, Cézanne and to name just a few.
He had amassed one of the largest impressionist art collections in Europe before he died in 1909.
Gachet, his wife and his home were the subjects of several pieces of art by celebrated artists including:  Dr Gachet, painting by Vincent van Gogh Dr Gachet, etching by Vincent van Gogh (1890) Paul Gachet, painting by , (1891) Musee D'Orsay Paul Gachet, painting by Émile Bernard, (1926 posthumous) Musee D'Orsay House of Dr Gachet, Paul Cézanne (1872)  
Portrait of Dr. Gachet is one of the most revered paintings by the Dutch artist Vincent van Gogh.
It depicts Dr. Paul Gachet who took care of Van Gogh during the final months of his life.
There are two authenticated versions of the portrait, both painted in June 1890 at Auvers.
Both show Doctor Gachet sitting at a table and leaning his head on his right arm but they are easily differentiated in color and style.
In 1990, the first version fetched a record price of $82.5 million ($75 million, plus a 10 percent buyer's commission) when sold at auction in New York.
When accounting for inflation, this is still the highest price paid for art at a public auction.