Privacy rights groups have called on Apple’s legal challenge to a secret U.K. government order asking it to backdoor an end-to-end encrypted (E2EE) version of its iCloud storage service to be heard in public, rather than behind closed doors.

The existence of the order emerged via press reports last month. Apple went on to confirm it was closing the Advanced Data Protection service to U.K. users. But the surveillance order requiring it to grant law enforcement access to data stored within the E2EE service is thought to include the info of users located outside the country, too, so it’s unclear whether Apple’s move will be deemed compliant. This in turn means a lot is riding on the appeal it’s filed challenging the lawfulness of the order.

Appeals on U.K. surveillance matters are heard by the Investigatory Powers Tribunal (IPT) — oftentimes behind closed doors. But, in a joint letter to the president of the IPT, rights groups Big Brother Watch, Index on Censorship, and the Open Rights Group call for the iCloud case to be heard in public.

“This case implicates the privacy rights of millions of British citizens who use Apple’s technology, as well as Apple’s international users,” they warn. “There is significant public interest in knowing when and on what basis the UK government believes that it can compel a private company to undermine the privacy and security of its customers.”

The IPT has a duty to hear cases in public unless doing so would threaten the national interest or the public, per the letter. But the three groups argue such conditions do not apply here. On the contrary, the public interest would be served by an open airing of the iCloud case, they suggest.