Yesterday Wizards of the Coast announced that all Professional Rules Enforcement Level draft events featuring Double-Faced Cards, like those in Shadows over Innistrad, will have the booster packs pre-sleeved.
This rule was first enforced at Pro Tour Shadows over Innistrad after there was some concern from the professional community about the potential competitive advantages garnered from certain seats at a draft table.
This rule change will effect Pro Tour Eldritch Moon, the 2016 World Championship, and the upcoming Grand Prix held in Sao Paulo, Sydney, Stockholm, Montreal, Kyoto, and Louisville.
Non-Professional Rules Enforcement Level events will still have players announce their Double-Faced Cards at the start of the draft.