How come someone from one boxing organization can hold a title from another?

Lets say Boxer A is in the WBC (World Boxing Council.) He weighs 190lbs, so he would be in the Junior Heavyweight division. He wins the WBC Junior Heavyweight Championship, yet also hold the World Boxing Organization (WBO)%26#039;s Junior Heavyweight title at the same time. How can they do this?|||They can hold titles in more than one weight class. It is perfectly allowed, it%26#039;s been done before by plenty of people. You just have to come back up or down to defend the titles against the number one contenders every six months. But it gets tiring very fast which is why things like this don%26#039;t last very long and they often choose to vacate one. Also after a while the two organizations will make you pick after it starts to affect their business. But as long as you the necessary defense it is allowed.