Out of interest how are there so many SAS books despite them being bound by a confidentiality agreement? Is it rarely enforced?
I'm not current and I can only comment on how the 'book' affairs were formally processed.
Firstly, to keep a perspective, 22 are not the only members of the SF community to be bound by the 'confidentiality agreement'. The matter also applied to predominantly NI based groups such as FRU and 14Int ( both since re-named ). Books emanated from the latter which are still keeping a host of NI lawyers busy. Is it enforced? It most certainly is. However, as background...............
The Confidentiality Agreement first came into real effect post Gulf 1. Those covered by this were initially "requested" to sign a non-disclosure form. This gathered momentum to the stage it became "compulsory" for regular serving personnel to sign. Some SF either chose not to or managed to deftly avoid the issue. Past members (now civvies) of these units also received a copy to complete and return.
An argument raised by the author Andy McNabb ( Steve) was that officers were permitted to write about campaigns under a 'Memoire' ruling while soldiers' writing efforts were described as being 'kill and tell'. In an effort to ameliorate the situation a department was set up within the MOD, known as the Disclosure Committee to vet ( redact? ) intended books. There are, for example, matters pertinent to NI that have - 30yr. 50yr, 100yr markers on incidents before they can arise for public viewing. Sensible personalities will proffer their manuscripts for review.
As for "enforced". The Hereford element who fell from grace were banned from ever entering camp/ MOD property. No big deal in several instances as gents tended to meet in local pubs and clubs, however, there were particular squadron and other festive occasions on camp which were out of bounds to them. That remains in place. On the humorous side, those PNG'd felt they should create a 'club' tie to display as a badge of honour.