I also just chatted with a CM on the DLR site:
Tina: HI justgot2havefun! It's a Magical Day at the
Disneyland® Resort! My name is Tina, what questions can I answer for you today?
justgot2havefun: I am planning a visit for May 21-24 and with the 24 Hr party, i expect it to get very busy.
justgot2havefun: My question is: What is Disneyland Resort's Capacity Closure policy?
justgot2havefun: Just in case it gets to the point that I may be denied entry during one of the few days I am in town...
Tina: During celebrations at the Disneyland Resort, the parks can be very popular. While rare, it is possible that we reach maximum capacity and guest entry may be temporarily stopped.
Tina: The best way to enjoy the parks during these times and avoid possible disappointment is to arrive early in the day, perhaps at opening time, and plan to stay in the parks the whole day.
Tina: While you may certainly exit the parks, re-entry is not guaranteed.
justgot2havefun: my understanding is the first stage of closure is to deny access to NEW guests while allowing those with hands stamped for re-entry in, where as the second stage would be to deny re-entry as well is this accurate?
Tina: That would depend on how busy the Theme Park is, and the time of day.
Tina: Once you leave the Theme Park, you would run the risk of not being able to enter again, because we cannot predict which guests will return, and when they will return.
justgot2havefun: thanks.