This is always the subject of rather heated debate here in France. I know one individual who scared the proverbials out of me on a flight from Montpellier to Lyon a few months back. We took off in VMC and there was VMC at Lyon, however, he got caught up in cloud as we crossed Nimes.
The guy had a PPL, saw the front approaching and had ample opportunity to land at an airfield or to fly around it. He told me that it was ok because we could still see the ground in patches. He just ploughed on and on eventually into full IMC for about twenty minutes. I felt totally out of control, having a only a basic knowledge of instrument flying procedures from my ATPL groundschool, which I am only studying (i still have no ppl)
I knew this guy only a short time, but have never flown with him since.
When I spoke about the incident with another pilot in confidence, he told me that it's just the way it is in France and that the rule is open to interpretation.