So why not Chatot? Why leave just one out?
Oh. Edit: Googled it.
Platinum FC: 4342 0595 5538
Heartgold FC:5286 8973 0818
Black FC: 0132 9951 7664
White 2 FC: 2495 2229 6740
Nintendo's bans are, as usual, completely arbitrary. There is zero reason for Sky Drop being banned since the glitch is fixed, Chatter and not Chatot should be banned, and most importantly as it actually matters in competitive gameplay, Soul Dew being banned is a beyond terrible decision for an über tournament. Latias and Latios are viable options in the über metagame with Soul Dew, far from overpowered, but aren't worth using without it. This has a very real effect on the tournament metagame (unlike banning Chatot), yet I'm sure of the fact that Nintendo didn't consciously choose to ban it for this tournament - they simply transferred their rules from their standard tournaments with übers banned, without considering that Soul Dew is not only not overpowered, but actually an important part of the über metagame.
I appreciate that Nintendo shows some support to the competitive community despite Pokemon being aimed at a casual audience, but their execution leaves something to be desired. They could definitely stand to get a more competitive-minded person to help run organised competitive play.