In a landmark decision, the panel decided that the Islamic wedding ceremony of Nasreen Akhter and Mohammed Shabaz Khan, which had taken place in a London restaurant, had "no legal effect".
Akhter had filed for divorce after their relationship ended in 2016, but the ruling means that she cannot claim money or property from Mr. Khan in the same way as a legally married spouse.
The couple have four children together and intended to follow the marriage ceremony through a civil marriage under English law.
But despite the fact that Ms. Akhter has raised the issue several times, the couple never addressed it.
Activists say the ruling will force Muslim women to go to "shady" sharia courts.
Pragna Patel, director of the Southall Black Sisters campaign group, said: "Today's ruling will force Muslim and other women to turn to Sharia" courts "which are already causing serious harm to women and children. to obtain reparations as they are now excluded from the civil justice system.
"What we are seeing is the outsourcing of family justice to unaccountable and fundamentally inspired religious arbitration systems. "
Ms. Akhter appealed to the High Court in November 2016, and the court ruled in her favor.
She obtained a "nullity decree" and the couple subsequently reached a financial settlement.
However, the case was remitted to the Court of Appeal by the Attorney General and the original decision was set aside.
Rolls Master Sir Terence Etherton, who examined the case with two other judges, said the Islamic wedding ceremony was not valid.
Announcing the court decision, he said, "The parties did not marry under the provisions of English law.
"The ceremony did not take place in a registered building. In addition, no notice was given to the Director General, no certificate was issued and no registrar or authorized person was present at the ceremony.
"In addition, the parties knew that the ceremony had no legal effect and that they would have to undertake another ceremony in accordance with the relevant requirements to be validly married. "