"I would insist that the valid set of moves for a unit are not dependent on the lack or presence of other units. I think if you order A Lon-Pic, even if there is no fleet in ENG, it is as valid a move order as any."
That's how Maslow argued it in our conversation before posting it to the community, too.
"So are you saying, Adam, that if Lon-Pic, and no F ENG, you would order that as invalid and therefore Holds?"
Yes, I would.
I should note, this is different from the common GM practice of not interpreting a unit's order based on the *orders* of another unit. What I'm suggesting is that I'm interpreting a unit's order based on the *presence* of another unit.
In a manner, I think this interpretation is a corollary to that of ruling A Bel-Par as invalid (which has been discussed earlier in this forum thread). According to the rules:
"An Army can be ordered to move into an adjacent inland or coast province... [or] across water provinces from one coastal province to another via one or more Fleets. This is called a "convoy.""
By this, we note that Paris is neither adjacent to Belgium, nor is it an eligible destination for a convoy. Therefore, A Bel-Par is invalid, and the unit holds. (Note: we assume that the above rule is complete).
So, returning to the impossible convoy of A BEL-NAF when there is no fleet in MAO, the rules state:
"If Fleets occupy adjacent water provinces, an Army can be convoyed through all these water provinces on one turn, landing in a coastal province adjacent to the final Fleet in the chain."
Combining the two rules, and beginning with the first, we note that North Africa is not adjacent to Belgium, so a direct move is (obviously) impossible. However, they are both coastal provinces, so a convoy could be possible. Unfortunately, switching to the rule for convoys across several water provinces, we can clearly see that there is not a chain of fleets between BEL and NAF. Therefore, assuming this second rule is complete unto itself, an army _cannot_ be convoyed when there are no fleets present to make the convoy.
The second rule does not conflict with the first, because the first clearly refers to coast-to-coast movement as a convoy and implicitly assumes that all pre-conditions for a convoy have been satisfied.
At least, that's how I see it
In closing, I want to clarify:
A BEL-ECH-MAO-NAF is invalid if there is no fleet in MAO.
A BEL-ECH-MAO-NAF is valid if there are fleets in both ECH and MAO, even if those fleets do not attempt to convoy the army.