Polo Rules

The very short form of the interference rule is that you can't make contact of the ball, unless another player is actively blocking you (by moving, stationary doesn't count). At that point you can then initiate contact with them off the ball.

That applies to defence and offence.

Would this mean that player A, riding alongside player B to create a moving block, is not allowed to make contact with B. Yet from that point player B is allowed to make contact with player A?