The BCA rule is this:But there is no inconsistency. The BCA rule is: The first ball contacted by the cue ball on each shot must belong to the shooter’s group, except when the table is open. ...
3.4 Open Table / Choosing Groups
Before groups are determined, the table is said to be “open,” and before each shot, the shooter
must call his intended ball. If the shooter legally pockets his called ball, the corresponding
group becomes his, and his opponent is assigned the other group. If he fails to legally pocket
his called ball, the table remains open and play passes to the other player. When the table is
“open”, any object ball may be struck first except the eight ball.
If you meant BCAPL (CSI), the rule is this:
2-5 Table Open After the Break
The table is always open on the shot after the break and remains open until groups are established. When the table is open, all object balls except the 8-ball are legal object balls. For combination shots, a ball of one group may be contacted first to pocket a ball of the other group. The 8-ball may be part of such a combination if it is not the first ball contacted by the cue ball.