Apple faces a challenge in its disagreement with the European Union regarding a tax-related issue.

According to a legal opinion from an adviser to the European Union’s top court on Thursday, Apple may be responsible for paying billions of euros in back taxes to Ireland, in a new development in a longstanding dispute.

According to a press release summarizing his opinion, Advocate General Giovanni Pitruzzella stated that the European Court of Justice should overturn the lower court’s ruling that the U.S. tech giant is not obligated to pay back 13 billion euros ($13.9 billion) in taxes.

In 2016, Apple expressed anger over the case being opened and CEO Tim Cook referred to it as “complete political nonsense.” Former U.S. President Donald Trump criticized European Commissioner Margrethe Vestager, who led the effort to eliminate preferential tax agreements and regulate major American technology companies, by labeling her the “tax lady” who harbors animosity towards the United States.

In 2020, the General Court of the European Union contradicted the European Commission’s accusation against Apple for making an unlawful tax agreement with Irish officials in order to pay significantly reduced taxes.

Pitruzzella recommended that the European Court of Justice reject the ruling and send the case back to the General Court for a new verdict on the substance.

The press release stated that the General Court made several legal mistakes and must conduct a new evaluation.

The judgments of the ECJ do not hold legal weight, but are frequently heeded by the court. The Court of Justice is anticipated to render its legally binding ruling next year.

Apple expressed gratitude to the court for its time and continued attention to this case. In a statement prepared beforehand, they stated that the General Court’s decision clearly stated that Apple did not receive any unfair advantages or state assistance, and they believe this should be maintained.

The European Commission has chosen not to give a statement. Their efforts to regulate the tech industry have grown to encompass investigations into Apple’s payment system and App store, as well as more stringent oversight under newly implemented digital regulations aimed at promoting fair competition.