Apart from P1’s prohibition against putting anything into the image area,

Why doesn’t TTG have any rules about labeling?

Because they aren’t necessary.

Viewers dictate that any publisher who uses the TTG label uses it well:

• If the viewer cannot figure out which image is being guaranteed TTG-qualified, the viewer will disregard the TTG label and will trust the photo publisher less.

• If the viewer cannot quickly identify a real person who is making the guarantee, the viewer will disregard the TTG label and will trust the photo publisher less.

• If the viewer sees that the photographer added anything into the image area (including the TTG label; see #1107), the viewer will disregard the TTG label and will trust the photo publisher less.

Publishers are always in the drivers’ seat