More "am paid to work". Different from "employed". Good example is a dive instructor; if you pay them then they're "at work". If you don't pay them, e.g. a club instructor like BSAC, then they're not "at work".
Must buy an M25 to M26 adapter if going to "Europe", or France at least.
Sorry for not being clear in my wording.
1) Employed divers:
I meant that a professional diver (commercial/military/public safety/sewer/research diver or an employed instructor or dm) probably requires that the employer provides them with safe (CE-approved, for a start) tools.
2) Independent divers:
An independent instructor could opt for non-CE equipment, because it is his own choice. Same applies to those who dive for fun or adventure only.
3) Not so rich divers:
If **** hits the fan and one needs to rely on an insurance, then one can only hope for that the insurance policy does not require one to comply with "safety rules" such as CE-approval and to only dive on dry land etc. etc. etc. If the insurance policy requires CE-approval and there is no free(ish) public health care available that includes recompression treatment, then non-CE gear is a risk.
4) Divers that are (or their employer is) responsible for the safety of customers:
A completely different thing is what is required from a dive buddy or a customer. If there is a customer, there is typically a duty of care, and allowing non-CE equipment to be used thus constitutes a risk: if an accident happens, then can you prove, that the customer was duly taken care of, and that (s)he was informed enough to dive with exotic gear, thus relieving yourself of responsibility (if even allowed by the law)? When a diver is dead, many questions rise.
A dive buddy might also be interested in the capabilities of the gear (especially breathing apparatus) if the dive is planned to exceptional depths or in a challenging environment.
An example: If I am diving to a depth of 30m/100ft in open water then I do not really care what kind of gear you use. Emergency ascent is possible and depth related issues are minor. However, if we ice dive in -1c or near freezing water and swim any significant distance from the entry point, then I DO REQUIRE that you have 1) two first stages, and 2) cold water approved regulators CE and ISO, and 3) dry air in dry tanks. If you do not, I dive solo.