Leaving Court for an Unauthorized Reason

[j51969]

A1, A2 set a screen near baseline in front court. B1 goes out of bounds to avoid the screen. Meanwhile the play developes to allow A an offense play. B isn't doing this intentionally to stop play like on the fast break case play. Would you:
1. Allow the play to develope and give A the scoring opportunity, and tell coach B to keep his player in bounds. (they may just not know they can't do that)
2. Call a violoation on B immediately. Spot throw-in and possibily give A an opportunity at a defensive turn-over.
3. Ignore it if B wasn't affected by the violation. Still say something to A coach at an appropiate time.