My principle, which I developed after thinking too much about it last week, is that if you happen to know a government secret (for a democratically-elected government) then it's morally both acceptable and right to leak it if and only if it reveals illegal behaviour on the part of some part of the government.

It is necessary for the government to keep some things secret. The people who elect and pay for the government generally have no problem with this. The problem is that the government itself is the entity that decides which things it's allowed to keep secret, so various government agencies can do things that they shouldn't and then use government secrecy to hide it. The possibility of anonymous individuals with conscience leaking evidence of this kind of thing, when it happens, is an important part of making sure it doesn't. So I fully support this old-school leaking.

It's the principle.

A good thing makes a good result, bad thing makes a bad result. A good thing is something that has enough truth inside it to transmit 'what is' accurately. Bad things have too much falsehood to see the things correctly.

imo you should judge things in the world for yourself after you've seen & confirmed what it is like.

Edit: @hugh3 hope that makes more sense