Once a taboo limit is breached, the inhibition is permanently eroded.

Evidence

A second conclusion is that the principal inhibition on the use of atomic weapons in limited war may disappear with their first use. It is difficult to imagine that the tacit agreement that nuclear weapons are different would be as powerfully present on the occasion of the next limited war after they had already been used in one. We can probably not, therefore, ignore the distinction and use nuclears in a particular war where their use might be of advantage to us and subsequently rely on the distinction in the hope that we and the enemy might both abstain. One potential limitation of war will be substantially discredited for all time if we shatter the tradition and create a contrary precedent. — Thomas C. Schelling, The Strategy of Conflict, 606

Categorization

• XREF: This is a non-recoverable governance resource: breaching a focal norm destroys it — analogous to what happens when a mafia boss breaks his own Godfather-bond; the enforcement currency is spent and can’t be reissued.
• DEEPTHINKING: The irreversibility claim — a coordination equilibrium, once broken, cannot be re-established because its existence depended on untested expectation — is a genuinely deep structural insight about norms and taboos.