Yes, but that does not show, or even loosely imply, that a candidatus has no value in terms of magical power, only that a mage has no claim to him as an apprentice before the Arts are opened. I've tried to emphasize that my position is irrelevant to this, but JL keeps returning to it as if apples proved oranges don't exist.
More, the phrase "may be punished" jumps out to my eyes. Are they using "may = might be" or "may = can be"? And if of no real value, then why would there be punishment? Can anyone explain why the loss of mundane property, one insignificant child, would be punishable?! I seem to remember quite a few recent posts that state, very matter of factly, that mundane theft is NOT punished, as a rule.
So if it's not mundane theft... hmmm... 
Fixed - the wording in the CoH is not "taking" but "depriving" - which is FAR more open-ended to interpretation. And apprentices are NOT the only examples of breaches of this section of The Code - loss of familiars, loss of physical magical items - admittedly just going from memory here, but I believe there are many different examples citable.
My issue with JL's claims is that he is presenting the absence of proof as proof of the contrary - that (in his own words) "You keep assigning value to a candidate before the candidate is an apprentice. The Code does not support this."
So what? I don't NEED the Code to support it - I believe it's self-evident, have tried repeatedly to demonstrate that. And because of that, yes - until someone cites otherwise (or can disprove my logic), I feel justified in my position. The Code does not support that my mage can snap his fingers or can sell his horse for silver - but I bet he can do both.
But perhaps that position has been lost in the babble. In homage to the classic Socratic style, I'll re-present, yet again, it as a series of propositions, with comments added below some - if any can disprove one of the propositions, let them. Otherwise... it cannot be but so. 
(And this is why ~I~ have never felt I needed to provide any "citations" or state "imo" - b/c nothing I'm claiming is anything but self-evident at face value. Unlike some other's assertions I've had issue with.)
And remember - "rights of claiming" are entirely separate and irrelevant. I'm heading toward the part of The Code re "depriving a mage of Magical Power".
1) Loss of vis is equal to loss of Magical Power.
(A mage with less vis has less "magical power" than the same mage with more vis. This is an important concept, and, yes, not every Tribunal will blah blah - but I believe the principle is sound enough to bring to Tribunal in the first place.)
2) My mage had property (slavery notwithstanding - I trust we've amply covered that issue).
3) My mage suffered a loss in property due to the actions of another mage.
(Note - NO ONE is saying the claiming was illegal - but in that claiming, I'm proposing that a different part of The Code was broken. That alone, a paradox over 2 parts of The Code, where the accused is following one part but breaks another, is not unheard of, and the one does not disprove or mitigate the other. And I can provide citations for this if anyone can't think of examples on their own.)
4) That property had value.
4.a) Now, if that value is mundane, equal to any grog, my position is weak at best. Fail.
4.b) If that value can be measured in Vis, then the complaint has merit.
So - what is the value of a candidatus?
5) A valid measure of the value of a thing is evidenced at face value by the selling price, that anything that can easily and readily be sold for vis therefore has a value of that vis.
6) A candidatus can easily be sold for a i[/i] price of, say, 3 vis. [i](This is based on a season of labwork work - an arbitrary but not inappropriate measure for a season for a mage. I am confident that a Gifted child can command such a price, but 1 vis would be adequate.
Even more evidence for this by citing any previous purchase of a [/i]candidatus by any mage for vis - and I bet that wouldn't be hard to find.)
7) Therefore... because my mage has lost property worth vis, he has suffered a loss of magical power due to the actions of the other mage.
That's my position, as clearly as I can lay it out. I don't need the Code to specifically "support" it because it only relies on the "depriving magical power" clause. And I don't have to qualify many of those with "imo" because they're either obvious or nut-and-bolt simple logic. My mage suffered a loss of property - imo... whatever. 