Jay Z Front and Center at Solange's Wedding White Party

Jay Z showed up to Solange's wedding Sunday in New Orleans breaking a cardinal rule ... but in this case there's an exception.

Hova and Beyonce arrived hours before the nuptials and Jay dressed to the nines in a fancy white tux.

Wearing white to someone else's wedding is normally frowned upon ... the whole upstaging the bride thing. But when you look at the photos it appears the ceremony has an all-white theme.