If settings are disabled, the user cannot enter "Reset" settings sheet and reset the device.
Note that there's no possibility to prevent some hardware actions, like entering the recovery mode, so if a user can enter the recovery mode, he may reset the device using recovery.
Another possibility is to use "Restrictions". Open the configuration details, "MDM Settings", and type no_factory_reset in the "Restrictions" field. Save the configuration to apply settings. This option works in MDM mode only.