The decision came from the Dutch justice, having been made known this week by the Netherlands Arbitration Institute, which belongs to the International Court of Arbitration.
The Dutch arbitration court justified the decision by stating that the operation made by the businesswoman to buy the stake in Galp "is null and void.
Thus, according to the decision to which AFP had access and is quoted by TSF, Isabel dos Santos will have to return the shares, worth about 420 million euros, to the Angolan oil company.
The Dutch court declared Sonangol the sole owner of the investment in Galp in the scope of the dispute between Sonangol and Exem Energy, a company owned by Isabel dos Santos.
After the decision was announced, the businesswoman said she will appeal the decision, stating that "Exem does not agree with the decision deliberated by the panel of three arbitrators who decided that only the allegations presented by Sonangol were sufficient, not having ruled on the evidence and documents presented by Exem's defense lawyers.