On macOS Sonoma and earlier versions of macOS, the spctl command line tool could be used to turn Gatekeeper on and off. For example, on macOS Sonoma the following command can be run with root privileges to disable Gatekeeper:

After running this command, in System Settings: Privacy and Security, you should see Gatekeeper displaying that it is set to Anywhere:

Also on macOS Sonoma, the following command can be run with root privileges to enable Gatekeeper:

After running this command, in System Settings: Privacy and Security, you should see Gatekeeper displaying that it is set to App Store and identified developers:

On macOS Sequoia, this Gatekeeper management approach no longer works. For more details, please see below the jump.

On macOS Sequoia, running the command to disable Gatekeeper produces the following output:

Globally disabling the assessment system needs to be confirmed in System Settings.

On macOS Sequoia, running the command to enable Gatekeeper produces the following output:

This operation is no longer supported. Please see the man page for more information.

In both cases, the Gatekeeper settings in System Settings: Privacy and Security should remain unchanged.