Is the same true in Ireland?
Not generally in the south. Although many (though not all) wholesalers etc. might want to confirm that you are an Electrician before selling goods to you, online orders from the UK or physical purchases in the north would negate the effects of this. So it is probably a matter of this individual being reported to the CER by a person or persons unknown.
If one doesn't have tight control of the availability of materials (and 'regulating' the imports would be particularly difficult), I doubt that, in practice, there is much hope of controlling what people other than registered electricians are getting up to. Yes, the occasional person might get 'caught', but that would only be a tiny tip of an iceberg.
Kind Regards, John