Wedding etiquette dictates that all men should keep their suit jackets on, until the Groom removes his jacket. It is helpful to any guests who may have their backs to the top table, for the Master of Ceremonies, or the Best Man to announce "Gentlemen, the Groom has removed his jacket".
Jackets should be kept on until after dinner, however it is more important that the Groom, the Best Man, the Ushers and other gentlemen feel comfortable, so it is best to act with attention to your specific environment. The Father of the Bride, the Groom, and the Best Man, will all feel more comfortable delivering their wedding speeches with jackets removed.