Ensure before proceeding that the $namespaceName and $className are correctly reference as it relates to your environment.
For all device settings, the WMI Bridge client must be executed under local system user (Administrator). To do that, download the psexec tool from https://technet.microsoft.com/sysinternals/bb897553.aspx and run psexec.exe -i -s cmd.exe from an elevated admin command prompt.
How to delete an Instance (AssignedAccess)
Delete existing instance
{
$obj = Get-CimInstance -Namespace $namespaceName -ClassName $className -Filter "ParentID='./Vendor/MSFT/Policy/Config' and InstanceID='AssignedAccess'"
Remove-CimInstance -CimInstance $obj
}
Ensure the right Instance ID is referenced. To see how this is done for Local account AssignedAccess, see https://techdirectarchive.com/2020/01/24/how-to-use-powershell-to-clear-assignedaccess/
To see how this command can be used to create, enumerate, query and modify an instance, see the following link and customise it to your need https://docs.microsoft.com/en-us/windows/client-management/mdm/using-powershell-scripting-with-the-wmi-bridge-provider
Kindly leave a commend below if you found other methods that worked(How to delete an Instance (AssignedAccess)).