Case goes to court - would the CAA stance stand up ??
Apart from the fact that the French are unlikely to know the ANO inside out, and even less likely to prosecute someone in France for violating the ANO for something that would possibly be legal on a French license, yes, this would stand up in court. It's not a CAA directive, interpretation or something. It's clearly written in the ANO.
Here is the relevant text of the ANO (Schedule 8, part A, section 1, subsection 1):
(1) Subject to paragraph (2), the holder of a Private Pilot's Licence (Aeroplanes) shall be entitled to fly as pilot in command or co-pilot of an aeroplane (...)
(2) He shall not—
(...)
(c) unless his licence includes an instrument rating (aeroplane) or an instrument meteorological conditions rating (aeroplanes), fly as pilot in command of such an aeroplane—
(...)
(iii) out of sight of the surface;
Oh, and remember the JAA is an organization without any legislative power whatsoever. Whatever they produce is a suggestion to countries to put it into their own law. A strong and very important suggestion, but a suggestion nevertheless.
This will only change when EASA takes over and issues regulation as part of the EU, which takes on legislative power immediately and across the EU. So you cannot point to JAR legislation saying something different than the ANO, because JAR doesn't have legislative powers. And you can also not point to French and other EU countries' implementation of the JAA suggestions into their own law and then claim that the equality factor should play a role. This is not (yet) EU regulated, so the whole equality thing doesn't work across borders.