...Station (GTS)? I have Pokemon: White, and I like to use the GTS, but I have to wonder if people can trade cheat Pokemon on there. I've gotten a few Pokemon from the GTS that were in master balls. I even got a level 99 shiny Exeggcute once from this.
Well, I put Pokemon up for trade, and get these shiny ridiculous things... Now they're making it so if you have a cheat Pokemon in your party and you try to do an online battle, it won't let you battle. So, if they allow cheat Pokemon to go through the trade station, then you're totally screwed when you try the online battle thing! Also, I've been reading that these cheat Pokemon can corrupt your game file, and a slightly corrupt file is not allowed on the battle area either!

So, part two of my question is does the GTS filter out the "cheat" from the Pokemon? I was able to attend and join in the Pokemon world championships after receiving the shiny 99 Exeggcute, and they didn't sense anything wrong with my game or anything... But I didn't use the Exeggcute as part of my party. What I did do was get an egg from it using Ditto, then release the thing into the wild.