Busch Gardens Williamsburg is one of three SeaWorld-owned parks that remain closed.
The new policy also bans face coverings with mesh material, which have become a favorite of anti-maskers.
Disneyland's theme parks have been closed since mid-March with no reopening in sight.
“I know this news is disappointing especially because this year we would be celebrating HHN’s 30th anniversary,” said Universal Orlando Resort president Bill Davis.
“You may remove your face covering while actively eating or drinking, but you should be stationary and maintain appropriate physical distancing," Disney's updated policy states.
The hard-ticket event will run for only two weekends from July 17-19 and 24-26.
Disney had previously said it would cut $900 million in planned capital expenditures due to the COVID-19 pandemic.
The rule change is due to the city of Winter Haven, Florida passing a face mask ordinance on Monday.
Orange County Mayor may ask Disney World to “reevaluate” reopening if COVID-19 outbreaks are tied to theme parks
Mayor Jerry Demings also said there's no indications that other reopened theme parks caused an increase in COVID-19 cases.