Set read-only permission on tickets
Allow a list of tickets to be considered read-only for non-TICKET_ADMIN users.
If you have any issues, create a new ticket.
Download the zipped source from here.
After enabling the plugin in your trac.ini:
readonlyticket.* = enabled
Add a section with the list of tickets to make readonly
[readonlyticket] ticket_list = 5,10,15
For Trac 0.11, you need to !add it to your permission_policies:
[trac] permission_policies = ReadOnlyTicketFilter, DefaultPermissionPolicy