AV states that Battle Standards have resist 50 all when deployed, but it says nothing about their total health. Can an enemy destroy them by picking them up out of the ground and breaking them in half?
If it breaks, how can it be repaired?
There is nothing hard and fast specific to battle standards written in the 4e rules that I am aware of. However, the Rules Compendium(pp 176-177) (and I'm pretty sure the DMG (p65) has this as well) has a table for the very purpose of attacking objects.
Here is the table from the online compendium:
In this case I'd probably go small or maybe medium. There is also a table for modifiers but they may or may not be relevant to trying to attack a battle standard.
Suffice to say you're looking at an AC/Ref of 5-8 a Fort of 8-10, immunity Will (as well as necrotic, poison and psychic) and HP between 10-20 (unless you choose to modify this with an HP multiplier, but that is up to you).
As far as restoring the standard after it is broken, the
I'd follow the rules for conjurations
The AV is pretty lithe on information, but it does say that any number of standards can be placed in a square and that they don't occupy a square, which is something typical of conjurations too. Thus, I'd rule as follows:
The Standard has defenses equal to its owner.
This makes the Standard work like a Shaman's spirit companion: you either reach the target number to poof it (in this case, 51 damage with a single attack), or you don't. Note that conjurations are immune to status effects, such as ongoing damage.
Addition: Note that each Battle Standard states:
This has some problems of ambiguous language of early D&D 4th edition: a
Given that they're full-priced magic items (not consumables) and the power is usable every encounter, I'd rule that any creature can pull them out of the ground, but that it simply ends the power and the player retains the item. Not terribly simulationist, but fits the rules of the game. I'd point out that most magic items aren't destroyed, such as weapons or shields or armor, in the course of their use. I don't suspect Battle Standards were intended to be much different from other similar rewards.
DM's should be free to adjudicate as necessary to fit their story, of course.