The main reason for a pilots order book is not to make unenforcable law but to cover yourself, and your company/club in the event of a negligence claim.
Exactly. I am just making the point of separating LAW and arse covering.
There is not a legal requirement for a pilots order book, it is not a legal document and any rules in it are not legal requirements. This include the 28 day rule.
So when a club insists on a 28 day checkout out it is not for legal reasons it is for club reasons and if the pilot is already LEGALLY entitled to fly having met the FCL/ANO requirements then one could argue they are perfectly entitled to be P1.........