How to allow/block content save ?

[Vince]

Hello,
Our web author plugin uses URLHandler and LockHandlerFactory extensions.
Our lock handler extends LockHandlerWithContext.

To put the editor in read-only mode, I can throw a lock exception from updateLock().
But if I return a false from isSaveAllowed(), nothing appends. The method isSavedAllowed is never called.

Is this method isSavedAllowed used ?

My needs is set read-only mode in case of the content is not the last version in serie. Using lock info is not relevant here.
What is the best practice do do that ?

Regards,
Vincent