Usually when you see the term BYOB, it means Bring Your Own Booze. Not in this case. When Serj Tankian wrote this song to protest the Iraq War, he meant it to mean "Bring Your Own Bombs". You could say this song compares to CCR's Fortunate Son from the 70's as far as it being a big hit that protests a war.
This song was a single off their 4th album Mesmerize. Fun fact, when they performed this song on Saturday Night Live, their lead guitarist let an F-bomb slip, and it accidentally made it to air! They performed another song later in the show with not similar accidents, thankfully!