(I read the requirements for trading between versions that a moderator gave me in another post, but I'm still running into problems)

My sister got me a Mew through a Gameshark-thing. (Not a real Gameshark, but one of the other brands of it) I beat the Elite 4 on Emerald and got the National Dex from Birch.

She got me the Mew in Sapphire. I want to trade my Mew from Sapphire to Emerald, so I can trade it to my FR/LG and raise it/have it there. Now that I've explained that, here's my problem:

It won't let me trade Mew from Sapphire to Emerald. It says Mew can't be traded now when I try, and I have the National Dex on both versions and have beaten the Elite 4 on both.

How can I trade from Sapphire to Emerald, so I can trade it to FR/LG?

The reason why you can't receive the Mew is because it was cheated for, and not obtained legally.

I believe I know the answer.

Because the Mew is hack and not legit, it will not let you trade it between versions. I don't know about obedience, as I never hacked Mew in Sapphire.

There is only one other Pokemon that does this, and that is Deoxys. Strangely enough, no other Pokemon acts up like this. (Deoxys obeys in Sapphire, but not LG, and can't be traded if non-legit...but in link battles it always listens.)

Maybe this is your problem?
- DNA