7 calls to drupal_is_denied() in Drupal 6

user_admin_access_check_submit in modules/user/user.admin.inc

user_authenticate in modules/user/user.module

Try to log in the user locally.

user_login_name_validate in modules/user/user.module

A FAPI validate handler. Sets an error if supplied username has been blocked or denied access.

user_pass_reset in modules/user/user.pages.inc

Menu callback; process one time login link and redirects to the user page on success.

user_pass_validate in modules/user/user.pages.inc

_drupal_bootstrap in includes/bootstrap.inc

_user_edit_validate in modules/user/user.module