I think it depends on the outcome of the case - I could see some possible resolution like the Swedish supreme court declaring that JSON counts as a public record and that forcing a block on prohibitive encryption of JSON endpoints offered by the government (assuming everything the OP said about constitutionality is correct).

We've seen such bizarre technical decisions from high courts before.

I dont think the swedish legal system uses precedents though. Does that matter?

I don't know - I think all legal systems use precedents to a certain extent - they're just extremely formalized in America and Britain. Sorry but I'm not familiar enough with their system to reply with confidence but I would say that if a high court in a country rules a certain way, even if that isn't binding to future rulings, it will cause people to adjust their behavior to avoid falling into a trap that's been clearly called out already.

Uh, also, IANAL.