Firstly, let me thank everyone who sent in emails. I did receive quite a few emails and was very pleased with the overall turnout.
I will endeavor to do a challenge related to every tournament I attend and potentially more often.
The first challenge can be found here.
Turns out, the specific question was ultimately invalid as Salamanders are NOT an infantry unit. DE Assassins can only be hidden in infantry units. This was something I knew and didn't think about at the time.
I did receive a bunch of answers that "he couldn't be hidden there" but they then failed to provide guidance as to the next step. I also received a few answers which actually dealt with the situation as if an assassin could have legally been in that unit.
In the end, I ended up with 2 answers that I really liked. 1 which handled the situation from the illegality standpoint and another which handles what to do in such an awkward situation (assuming it was legal). I've decided to send both emailers a pack of cards.
Answer 1 - Tarjei Aasen
Shadowblade cannot join Salamanders as they are not infantry or war
machines (they are war beasts). If a player at a tournament I ran had
written down that Shadowblade was hiding in a unit he couldn't join,
I'd rule that he would not show up for that battle, but would award no
VPs to the opponent.
Answer 2 - Joe Rogers
I would just rule he could not reveal himself. The reason being that if I allow him to be revealed, then I have to follow it up with an arbitrary decision since this for sure isn't covered anywhere in the rules.
So no reveal = I don't have to make up my own rules.
Allow him to reveal = I have to make up my own rules.
So I'm taking the KISS approach.
If you want more ammo for the ruling, you could say since they didn't cover this pretty common situation in his unit entry, that they didn't intend for it to be possible.
Fluffwise you could say he is swept away with the unit, but you could justify any garbage answer you want fluffwise.
I loved answer 1 from Tarjei as it is ultimately the correct way to handle the situation.
I also loved answer 2, from the "Rodge", as it is a great approach to handling rules debates for situations not covered by the rulebook. Simple yet brilliant approach IMHO.
Congrats to both winners.
Thanks again for all the entries.
I look forward to the next contest.