I honestly don't know the finer details of it.
But - I would have thought that it is technically possible for a health professional to decide someone is unfit to drive - I get the feeling that this is one of the situations that SDG's Dad is concerned about. This is something that MIGHT (might not) happen. Is he in a fit place to deal with that news, if it is the case?
I would have thought that a suicide attempt alone would not be enough to justify a ban from driving on medical grounds - but I would have thought that you would have to have a green light from a professional to drive a car again afterwards (I have no idea how this would be worked out, but this is not a unique situation and I'm sure that these are questions health professionals in these circumstances will face regularly).
I don't know where normal concerns re finances end, and obsessive behaviour starts so I was just a bit concerned when SDG mentioned that his Dad now seems to be "fixated" on this issue. Given the history, and the fact that SDG's Dad is still in recovery, it just struck me as a bit of a warning.
I do think that this is one to deal with with the health professionals first, whilst some anecdotal stuff on hibs.net is all well and good.
They should be able to give him appropriate advice on the technical issues regarding how insurance, getting back behind the wheel etc works, but more importantly give him advice on how best to communicate any of this with his Dad.