How should you react, as an AL player, when a Dungeon Master alters the rules?

Question

Let's say you're an Arcane Trickster Rogue, and you play in Adventurers League games. One night, you play at a DM's table, and during combat, when you would normally benefit from Sneak Attack, said DM tells you that you don't benefit from it, as "it would be too powerful with the magic given by the Arcane Trickster archetype".

Or let's say that you are a Small creature wielding a Lance, but the DM says that “you only deal 1d8 damage instead of 1d12 with it because of your size”.

These scenarios are only examples, but they share the idea of an AL DM blatantly altering existing rules. While it is generally seen as bad behavior to interrupt the game flow in order to point out something to the DM, are such situations (where the DM clearly alters the rules in a non-homebrew session) worthy of stepping up as a player at that moment ?

In other words, how should you react, as a player, when existing rules are modified by the DM in Adventurers League organized play (provided that you double-check beforehand that the rules were indeed altered)...

1. Point out the alteration immediately to the DM and politely ask him to stick to the rules -- but then if he refuses...

   A) Accept it and do nothing

   B) Go speak to the organizer (either now or at end of session)

   C) other

2. Write it down to mention it to the DM during break time or at end of session (even if the rules alteration severely impacts the game at the moment)

3. other

Answer 1

tl;dr: The DM is not permitted to use house rules in Adventurer's League, hence it is legit to "complain" if (s)he still makes such changes.

The D&D Adventurer's League Player's Guide has a section "D&D Adventurer's League Code of Conduct". It states (among other things):

Follow the DMs lead, avoid arguing with the DM or other players over rules.
[...]
The organizer has the right to remove a disruptive or aggressive player or Dungeon Master from the play area or premises.

Generally, that indicates that you should not argue with your DM about the rules. If there is a serious problem with your DM, the organizer should take care of it.

However, the FAQ state:

House rules, that is to say rules that you create that aren’t in the official materials such as critical fails, new races, new classes, etc., aren’t permitted for use in play; the Adventurers League uses the rules as presented in the PHB.

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Therefore, I would suggest that - after the session - you show your DM the (official!) FAQ document linked above and point out to him that, while he can change the rules in these ways during regular play, it is not permitted during Adventurer's League events.
If the rule changes are more severe, you can also talk to your DM during a break. I would advise against starting the discussion during the game, unless it's a life-or-death situation.

Should your DM refuse to acknowledge the clarification in the FAQ, you can talk to the organizer to handle the situation, as mentioned in the Code of Conduct.

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I would recommend that all your players (including the DM) read the AL Player's Guide, the FAQ, and the DM also the AL Dungeon Master's Guide. All of these documents can be found here, as well as some additional documents.

_{^{Note: all emphasis mine}}