they may have a case if its an health and safety issue.normally you may be required to put tape around the ring so theres no way of getting the ring caught.depends really what job you do.
Yes, they can if it is proven to be a H&S issue... However, in years of work I have never heard of this being enforced. Normally taping up the ring is acceptable.
It does depend on your job - is there a chance your ring could be caught in machinery? If so, there is a very real possibility of you losing your ring finger.
Suggest, as previous respondents have advised, applying tape to your ring, and see what your employer says.
I never wear a ring myself as it would be dangerous in my work. I've seen a few accidents in my time, people hanging by their finger or burning by shorting out car electrics etc. so if you value your health follow your employers sensible advice otherwise you can be prosecuted for ignoring Health and Safety issues.
Many employers who use machinery on their premises ban the wearing of jewellery for health & safety reasons in case in either gets entangled in the machinery, or falls off and causes product contamination. (If you worked in a food factory for example, it could possibly fall into a product and somebody might subsequently choke on it). Usually a wedding ring or similar symbol of religious significance is permitted to be worn provided it is taped over. They will not have imposed such a regulation to be difficult but specifically to protect employees from accidents (for which they could possibly be sued).