Guns N' Roses fans were forced to take sides in the legendary war between Axl Rose and Slash -- after security at a recent GNR show banned fans from wearing Slash gear inside the show.
It all went down at the GNR show in Canada last Wednesday -- concert security informed fans that they were required to turn their Slash t-shirts inside out .... and leave their top hats outside.
TMZ spoke with a member of the concert security team who confirmed the marching orders -- and told us the instructions were passed down from a producer for the band.
We're told a few fans took the high road and went home ... but most just sucked it up and did what they were told.
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