Catcher's Interference in Baseball: Rules & Implications

Question
We played a game in which the catcher came in front of the plate before the pitch crossed over While executing a pitch out.  Is this legal?

Answer
If the batter swings or appears to attempt a swing (starts his swing in any way) this would be catchers interference.  In that situation, the ball is dead immediately and the batter is awarded first base (runners go back to the base occupied at the time of pitch unless forces to move up by the batter taking first base).  If the batter makes no attempt to start a swing, there is no call and the ball remains live.