My friend is running an Enraged Battle Ox/Winged Beast-Warrior Deck and I was wondering about the ruling of this card.

Berserk Gorilla (IOC-013)
Attribute: EARTH
Type: Beast
Level: 4
Attack: 2000
Defense: 1000

Card Text:
If this card is in face-up Defense Position on the field, destroy this card. The controller of this card must attack with this card when possible.

Can Berserk Gorilla attack during the first battle phase of the game. Here's an example of when the conflict and question first occured:

-Duel Opening-
+My opponent went first.

-Opponent Turn 1-
+Main Phase: Summon Berserk Gorilla in Attack Mode.
+Main Phase: Set 2 Magic/Traps.
+Battle Phase: Berserk Gorilla is forced to attack due to effect. 2000 LP Damage.

My final question is this; Is this action legal? We re-started the duel because we couldn't come up with a solution, but I recently fed his deck with two more Berserk Gorillas (in exchange for an Archfiend of Gilfer and a Big Bang Shot). So I want to clarify this ruling ASAP.

Berserk Gorilla can only attack when he is able to. Since the very first turn of the game you are always unable to attack, Berserk Gorilla is unable to attack, and does not have to attack.

Berserk Gorilla's text includes:

"The controller of this card must attack with this card when possible."

Since it's not possible to attack on the first turn, the Gorilla has to wait.

VenomLord is correct (as usual :)), Beserk gorilla's effect only comes into play when he is able to attack, like if your opponent has a Blue Eyes or Dark Magician out, Beserk still has to attack. Some times when he is unable to attack, Swords Revealing Light, Opening turn if you go First, Spellbinding Circle, etc...

Many thanks on helping me out with my conundrum of a question. I appreciate it. Feel free to send me any Private Messages if you have questions of your own, or if you think there is a thread I might be interested in looking at.