Few have gotten a glimpse of Pablo Picasso’s “Head of a Young Woman,” an oil painting he created during his “pink period,” featuring a woman with long, raven hair and a sideways stare. For years, it has been in a Spanish billionaire’s private collection on a private yacht anchored in the Mediterranean Sea.

Nearly 40 years ago, Jaime Botín, whose late brother Emilio Botín once headed Spain’s Santander Bank, bought the painting. But it’s now sitting in Madrid’s Reina Sofia Museum where Spanish authorities are holding it.

Spanish police flew Tuesday to the French island Corsica to retrieve the painting, a $26 million masterpiece dubbed a “national treasure,” which is not permitted to leave Spain — Picasso’s home. French customs agents had seized it from Botín’s yacht last month when his son, Alfonso, took it to Corsica, according to NPR. Authorities there said they got a tip that Botín intended to smuggle the painting to Switzerland and sell it and, when agents asked the boat’s captain for documentation that the export had been approved, he was unable to produce any, according to the Financial Times.

“We found the artwork on the boat already packaged up,” French customs agent Vincent Guivarch told reporters. “It appeared ready to be shipped.”

The painting has become a window into a much larger battle between art collectors who want the freedom to do with their art what they please and countries that want to hold onto their histories.

Many counties have bans on art exports. For example, the U.K once slapped a temporary ban on a famous Picasso painting. Understandably, some countries want to keep their most prized possessions at home. Germany and Ireland are considering new export laws. But opponents argue such bans anger art collectors and hurt the art market — and the art.

“It’s a real problem,” Michele Casamonti with Tornabuoni Art said last year, according to the Financial Times. “The rule in Italy is that any art over 50 years old cannot be exported without a license, whatever its value. So works made in the 1960s — notably by the highly sought-after Arte Povera artists — are increasingly falling under the legislation. And something that is not exportable can lose over 50 percent of its value, since it can only be sold on the domestic market.”

As for the “Head of a Young Woman,” the little known painting is caught in a contentious legal dispute between Botín and the Spanish government.

Botín, 79, is heir to Spain’s most lucrative banking empire, according to Forbes. His great-grandfather founded Santander — a family business run by his grandfather, father and then his brother. Botín once served as vice chairman while his brother was chairman but stepped down in 2004 to invest in the Spanish bank Bankinter SA, where he is now the company’s largest shareholder.

In 1977, Botín bought the Picasso painting at the Marlborough Fine Arts Fair in London, according to the Financial Times. In 2012, Christie’s Spanish branch requested permission for Botín to have it exported to London. The next year, Spain’s culture ministry said no, claiming the work, which dates back to 1906, was important to the country. It was considered a national treasure.

Spain’s National Court has since upheld the Culture Ministry’s decision. That ruling is now on appeal to the Spain’s Supreme Court, the Associated Press reported.

“The law says that if the artwork is more than 100 years old and has national cultural significance, the owner needs to apply for permission to take it abroad or sell it,” José Castillo, a national heritage expert at Spain’s University of Granada, told NPR.

Botín responded with a few arguments, one being that the painting was not on Spanish land; it was on a boat that sails under a British flag. It’s the same argument his lawyers are currently using to defend the recent export attempt.

French customs agents seized the painting July 31 and alerted Spanish authorities, believing Botín had given up on the legal proceedings and decided to sell his painting secretly. On Tuesday, Spain’s Guardia Civil, or Civil Guard, flew to Corsica with members of the Ministry of Culture to retrieve it. Police took it to the Reina Sofia Museum for safe-keeping until the legal dispute is resolved.

Botín’s lawyers said he did not disobey Spanish law because the painting’s permanent home is on a yacht, named Adix, which is registered in the United Kingdom, according to Bloomberg.

“The painting was painted abroad, purchased abroad and has since had a permanent address abroad,” attorney Rafael Mateu de Ros said in a statement, according to Bloomberg. “Therefore, it could have not been exported, legally or illegally.”

“For years now, the picture has been inside a British vessel, which is foreign territory for all who that may concern, even when it is moored in Spanish ports,” he said, according to the New York Times.

If Botín is found to have broken Spain’s art export ban, he could face more than $600,000 in fines. Or the Spanish government could take ownership of the Picasso away from the billionaire.