Currently any calls to the /data/wow/guild/{realmSlug}/{nameSlug} endpoint on the profile-classic1x-us namespace return a 403 error no matter the authentication used.
{
"code": 403,
"type": "BLZWEBAPI00000403",
"detail": "Forbidden"
}
A big issue as a lot of outside tools that players rely on use these endpoints to provide services for applications.