Are alternates allowed in parity? If they are not, it is easy to circumvent the rules. Alternate player just needs to be rostered as a full time player and revert back to alternate status after parity is over. How is this policed and what are the penalties?
Are alternates allowed in parity? No
How is this policed and what are the penalties? It's not and there are none unless your team knocks the IHC or MMF from black. If this is the case, DNA samples are required to prove the identity of all players. If the league still isn't satisfied, the tournament rules will be adjusted and games thrown out to ensure proper placement of these org's.
Discounting the conspiracy theorists who believe any alternate is there simply to cheat, there are some really valid reasons for alternates to play, especially considering the Fed does parity in April & May. Perhaps the regular player has a family commitment, other sports, roster isn't full, etc. I've seen many a kid not on a roster dress and play in parity. Most coaches keep keep the missing kids name on the roster and the alternate plays as that kid.
At the end of the day, try and keep some perspective. This is still nothing more than a youth hockey tournament (and $$ grab) and it's not worth getting all twisted in knots over. Except for the youngest of ages, an alternate or two isn't likely to make a silver team into a black team.