User blog comment:V3hemenc3/Runic Bulwark and who on your team should build it/@comment-75.147.10.230-20130201184330/@comment-5889958-20130201190352

Any 2 same aura can stack, meaning 2 bulwark can stack as well. However, only the 2 aurabearer would benefit from it.

Right now, if you got aura item, and someone in your team get that same item, you get your aura applied to yourself, and you would also get the same aura from the other teammate and vice versa for your other aurabearer teammate.

However the rest of your team gets only 1 aura applied at max.

http://leagueoflegends.wikia.com/wiki/Aura