I'm not sure there is an official Disney policy or rule. But, the word on the street, as noted by the PP, is 30-45 minutes before park opening is when you are let in and held inside the park by CMs.
Our Authorized Disney Vacation Planners are here to provide personalized, expert advice, answer every question, and uncover the best discounts.
Let Dreams Unlimited Travel take care of all the details, so you can sit back, relax, and enjoy a stress-free vacation.