Mr. Downing is wildly incorrect.  I suspect he may be thinking of Junior A not major juniors.  Playing major juniors causes a player to lose his ability to play NCAA hockey.  There are some rules (I don't know the details) where a player who plays a limited number of games forfeits some eligibility but is not completely ineligible.  The vast majority, however, of such players can never play college hockey in the US.
 
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