Typical thread of the two sides battling it out, neither changing their mind.
The fact is there is nothing in the law to prohibit it.
In law, that is all that matters. In court, that is all that would win the case, open and shut.
If the part fcl said someone who has previously held a licence may not fly solo until that licence is valid once more, fair enough, but it really doesn't say that anywhere.
As head of training you are free not to send people solo, just as others are free to send them off.