It is only a court that can determine that a risk assessment is or is not suitable and sufficient. However, it is the enforcing authority who will or will not contest it. If the enforcing authority are of the opinion that the RA is not suitable and sufficient, the onus is on the Responsible person (assesssor) to demonstrate the reasonableness (Is that a word??) of it.
"Article 34. In any proceedings for an offence under this Order consisting of a failure to comply with a duty or requirement so far as is reasonably practicable, it is for the accused to prove that it was not reasonably practicable to do more than was in fact done to satisfy the duty or requirement".
(Providing, of course, that as a result they have put someones life at risk)
Also, It is still the duty of the Responsible person to ensure that the RA is completed (in most cases the employer). However, are the shop staff competent to undertake a suitable and sufficient RA? From the evidence I have seen, most RA don't even pass the first hurdles - Who are the persons especially at risk? Without it - not suitable and sufficient. The same goes for most generic head office produced lip service risk assessments
IMHO