It's the opponent's Main Phase 1. I use my Wind-Up Rabbit's effect in response to a Dark Hole and the Opponent chains Book of Moon, targeting Wind-Up Rabbit. We all know Wind-Up rabbit gets banished Face-down, so this is not the problem. After that, the Opponent Special summons Dark Simorgh, it prevents cards from being set. He attacks and ends his turn. It is now my Standby Phase. Since Rabbit has to return to the field in face-down defense position, but Simorgh doesn't allow me to set, what happens?

It is still setting the monster, which you cannot set. "Wind-Up Rabbit" gets sent to the graveyard. A monster that is placed on a field face-down is set. And the reason "Wind-Up Rabbit" doesn't have set anywhere in its text is because it returns to the field in whatever position it left the field.

This has been asked many times before, honestly, I don't know what to answer you. There has been a conflict for this ruling due to the fact that some admins in DN say that it is not returned to the field and remains banished. Others, state that it's returned to the field normally because it doesn't officially state it's "set" and is actually "face-down" so he returns. Reaper of the Cards states that he is not returned to the field because of the Time-Police dilemma vs Dark Simorgh. Other admins like Minako state it's not like that and is returned normally. Honestly, I'd leave your dilemma to our judge Syrufit or our ruling genius Niko327.

Though, if it were me who is answering I'd say he returns normally as he is not being set. Dark Simorgh's effect doesn't allow setting cards, you're not setting him, he's just returning flipped face-down, he's not being set. Though, I'm not sure.

Rabbit would end up going to the grave, even though it doesn't specifically say "set", any monster that is placed face-down on the field is Set.

I already knew the answer, however there's no official Konami document that states so yet.

I'm guessing it's the same as when you have 5 monsters and Rabbit tries to return, it's sent to the grave.

It gets sent to the grave

http://forum.duelingnetwork.com/index.php?/topic/50546-wind-up-rabbit-vs-dark-simorgh/

TCB more trustworthy than Reaper

It certainly doesn't come back. What I said in the topic was prior to research. It's a debate between "It remains banished" and "It's sent to the graveyard".
As Gig said the most obvious choice would be for it to be sent to the graveyard, according to the 5 monster ruling. But, according to Space Time Police's ruling (that Reaper mentioned), it stays banished. So I'm not sure on this one.
Personally I would say it goes to the graveyard, but it's not 100% sure until Konami releases official documents.

This is definitely a tricky one, but I'm actually leaning the other way from all of your opinions of it getting sent to the grave/staying banished.

http://yugioh.wikia.com/wiki/Return

Based on the rulings of the "Return" mechanic, it ignores most conditions and restrictions considered in other mechanics. The act of "returning" a card to the field, hand, deck, whatever, is literally just returning. It is NOT considered a Summon of any type,and neither is it considered "Sending" a card to anyhwere. It is simply "returning" to its former placement.

While the return mechanic actually favors Wind-Up Rabbit returning safely, it never specifically says anything about it also being considered or not being considered a "Set." Looking under the Summon mechanic, there is no mention of "Set" either, but the mechanic of "Set" is something that really can only happen when the game state is open, unless a card effect that activates specifically says to "Set."

According to the game mechanics of "return," I'd say personally Rabbit returns safely to face-down defense position, but really it's Konami's place to say if return is able to over prioritize continuous field effects, which is where it gets iffy since there really is no mention of it.

According to the Wiki:
http://yugioh.wikia.com/wiki/Set

To Set (セット, Setto) is to place a card on the field face-down.

Setting a card on the field = placing a card face-down.

Syrufit wrote:According to the Wiki:
http://yugioh.wikia.com/wiki/Set

To Set (セット, Setto) is to place a card on the field face-down.

Setting a card on the field = placing a card face-down.

Yes, and that's where it's a bit tough to say because Return ignores many other mechanics in other situations. It could possibly be simply moving it. Iunno man, either outcome is logical, but which actually happens, I couldn't say.

Returning to the field only ignores the summoning mechanics. Setting =/= Summoning

yah you're right. I was basing my argument on the fact that returning ignores a lot of game mechanics, but since there really is no mention of it not being considered a Set, we have to assume it to be false. At least, that's the science of logistics. Assume false until proven true. But, I think you're probably right at this point, unless Konami comes out with a specific ruling on the case that says otherwise.

I would agree it's sent to the grave if it doesn't come back to the field. The way I see it is that in the Space-Time Police situation, the effect doesn't even have the chance to resolve due to it leaving the field to a place it can't resolve itself. On the other hand, Rabbit itself CAN resolve and attempts to, but Simorgh prevents it. STP = the card itself prevents resolution. Rabbit/Simorgh = Rabbit is prevented resolving from another source.

I guess this'll have to stay unlocked until Konami gives us a source. :/
If we base it on Space-Time police, then Rabbit Stays banished, but if we base it on the 5 monster scenario with Rabbit, it goes to grave.

I'm guessing it's the second scenario, since it would pretty much be the same. The card can't be returned to the field in either case so it's sent to the graveyard. Err... Konami tells us all to f*** ourselves.

Also, the only reason the Space-Time Police ruling is different is because Space-Time Police does not return, but merely set the monster. Or at least I think so.

No

Space time thing shouldnt be used, as its specificly says Set, and Rabbit just says return

But the rl and DN rulings have been decided that it is sent to the grave

Vongola Decimo wrote:No

Space time thing shouldnt be used, as its specificly says Set, and Rabbit just says return

But the rl and DN rulings have been decided that it is sent to the grave

Irl, depends on how the judge rules it. DN, depends on how the admin rules it. There's no official ruling yet.

Also, ST Police specifically says set, however, setting a card on the board is placing a card face-down, so technically, if rabbit returns face-down, it's being set.