No, I am pretty sure you'll find that is not true. For whistleblowing, many countries, including mine, have legal protections. This is to encourage people to make conscientious decisions to release information in the interests of the greater good. I've had an (admittedly super quick) look at Italian laws too, which are due to change in this area this month.
The State is not a tyrannical apparatus like in Orwell's 1984, where the slaves-citizens must obey.
They State is us. Me, you, them (the political bodies).
The political bodies are to be held accountable if they violate international law on human rights, on crime against humanity.
It's them who commit high treason, not the whistleblower.
Accessing information through illegal means via conspiracy (something Assange is accused of) is not covered by this. Nor would it give him protection in instances where information was released which is not covered by whistleblowing legislation.
Wikileaks was somewhat the equivalent of a game of 52 pickup. If the picture cards are legitimately evidence of illegal activitity, that still leaves a lot of ground to cover in terms of the release of other information through a widescale public release (rather than in a more controlled fashion).
In my country it is covered by this. It's called scriminante.
If I break into someone's else office and steal documents that prove that someone (Mr X) murdered tens of people, there will be a trial and I will be judged but there will be the scriminante (force majeure) that will excuse me.
So I will not go to jail.
Because the murder of tens of people is 100 times more serious than breaking into someone's else office.
To be clear, I'm not suggesting he's guilty of anything. The case is multi-faceted and tiring, honestly. But it's a little simplistic to suggest his actions wouldn't be illegal in (for example) Italy.
In Italy there is the fair trial.
There is not the Inquisitorial System of the Anglo-Saxon countries that prevent people from defending themselves.
That is, the judge decides what can be dealt and what cannot.
Assange would never be imprisoned in Italy, because his lawyers would crush the accuse like a cockroach, in court.