Local users can sudo as expected however sudo is not working for Active Directory users on AIX
In this case sudo was not compiled with either pam or aixauth support.
Run "sudo -V" and look for Authentication methods. The following are some examples of output:
Authentication methods: 'aixauth'
Authentication methods: 'passwd'
Authentication methods: 'aixauth' 'pam'
The "aixauth" is standard AIX authentication and what will be used if the system is configured for STD_AUTH (you can check the login.cfg file to see what is set). The "pam" will be used if login.cfg is set to PAM_AUTH. The "passwd" auth method is only looking in the passwd file and will not work with authentication services.