Permission for a group to enter Chrischurch's cordoned-off Cathedral Square has been revoked by officials who deemed it a political event.
A member of the group contacted the Canterbury Earthquake Recovery Authority this week asking to go in to check the condition of a riverstone cairn.
The authority's chief executive, Roger Sutton, granted permission on Tuesday but revoked it on Thursday morning.
Mr Sutton said he gave permission based on the request to check the cairn and arranged for a staff member to escort the group into the red zone.
In 2010, elected councillors were replaced with government commissioners.
The group of about 12, led by Green MP Eugenie Sage, planned to place a wreath on the cairn marking what it called the commemoration of the loss of regional democracy in Canterbury and had invited media.
Mr Sutton said in light of this information, the authority reconsidered its permission because it was deemed to be a political event.
An engineer linked to the group was allowed in to do an assessment of the cairn.