Law is something that comes from primary and secondary legislation, or in some cases Common law. Legal precedent, often referred to as case law, if it has come from a court of record, is guidance on interpretation of said legislation which can still be superseded by another court. Case law is often, but not always, pertinent to a particular set of circumstances and not a generalisation.
It is not a FEO’s job to interpret legislation, that is the preserve of the courts, any more than it is your job to interpret any legislation.
Whilst training is certainly a good idea, if such a condition be imposed then it must be clear to any applicant at the very start of the process. The requirement must also be ethically and educationally valid. As others have alluded to there are many other countries that have just such.
Playing devils advocate, in all the years we’ve the firearms and shotgun legislation, how many deaths are caused on an annual basis as a result of lack of ‘training’? IIRC it is about two deaths a year from legitimate firearms users, whilst unfortunate statistically insignificant in a population of nearly 70 million.