An appeal has been lodged against a landmark ruling by the Malaysian High Court that a Sarawak Muslim can officially convert to Christianity.

The National Registration Department (NRD) filed its appeal against Rooney Rebit, 41, just ahead of the 24 April deadline. The reasons for the appeal need to be revealed within eight weeks.

Rebit was born into a Christian family that converted to Islam when he was eight years old. In March a High Court ruling said that he was too young to choose to convert at that time, but that when he chose to become a Christian at 24 he was mature enough to make his own decisions.

The High Court ruling requires the NRD to issue a new identity card – which, to date, it hasn’t done – showing his first name only and with his Muslim classification removed. If the NRD’s appeal is upheld it might make it harder for Muslims to change their religion in the future. A constitutional rights lawyer said: “Judges are abdicating their role to protect the freedom of religion in the Constitution.”

Rebit’s case reached the High Court when the NRD insisted that a Sharia Court needed to authorise removing the word “Islam” from his identity card. The High Court judge said Rebit’s case was not one of jurisdiction, but raised constitutional issues regarding his right to religious freedom. “He does not need a Sharia-Court order to release him from Islam, because freedom of religion is his constitutional right and only he can exercise that right,” the judge said.

The NRD was the only one of three involved bodies to appeal against his victory: the Sarawak Islamic Religious Department and Sarawak Islamic Council did not lodge appeals.

The majority of the population of Sarawak – one of two Malaysian states on the island of Borneo – is Christian.