Add folders to trusted locations from Office Button | Access Options | Trust Center | Trust Center Settings | Trusted Locations.
The entries are stored in the registry under the following keys (where N is the number of the Trusted Location, starting from 0).
The registry settings can be set on a per-user basis using Group Policy or a registry/reg batch file. You can also set registry keys using VBA within Access, but that will only work if the database is already in a trusted location.
Access 2007: [HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Access\Security\Trusted Locations] [HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Access\Security\Trusted Locations\LocationN]
Access 2010: [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Access\Security\Trusted Locations] [HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Access\Security\Trusted Locations\LocationN]
Access 2013: [HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Access\Security\Trusted Locations] [HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Access\Security\Trusted Locations\LocationN]
For each trusted folder an entry with following registry keys may be populated:
Path: Path of trusted location, ending with \ (reg_sz)
AllowSubfolders: Determines whether subfolders are trusted as well (0=No; 1=Yes) reg_dword.
Description: Optional text description (reg_sz).
Date: Date of last update.
You should not designate a public folder on a network share as a trusted location, apply appropriate NTFS permissions.
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Access\Security\Trusted Locations] "AllowNetworkLocations"=dword:00000001
[HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Access\Security\Trusted Locations\Location0] "Path"="\\\\server64\\foldershare\\" "AllowSubfolders"=dword:00000001
REG - Add a registry key
REGEDIT - Add a registry file
Compatibility Between the 32-bit and 64-bit Versions of Office 2010 - MSDN