IN THE NOT-TOO-DISTANT FUTURE, NEXT SUNDAY AD: Ancapistan has been established in what is today Switzerland. There are competing defense agencies, but they have formed a defense cooperative to fend off a potential attack from, let us say, France, the government of which is highly disturbed to have an example of successful anarchy right next door.
The "Swiss" defense plan involves elaborate traps set along the "non-borders" for any invading army. They ought to work, but whether they will do so depends greatly on their being unknown to the enemy.
A French invasion looms. On its eve, a resident of Swisscapistan informs you that he has (through legal but perhaps sneaky means) obtained the entire Swiss defense plan. Furthermore, he hates this anarchy crap, longs for a good old-fashioned boot on his neck, and intends to send the plans to the French, meaning the certainly Swisscapistan will fall to the upcoming invasion.
Are you, or anyone else in Swisscapistan, justly permitted to prevent this disclosure by force or by the threat of force?