HDMI.org has deemed adaptors that enable easy transmission from Apple laptops illegal as they do not follow HDMI specifications.
In a report by TechRadar, HDMI.org reveals that all HDMI cables undergo compliance testing specifications and since the adaptors don't have any compliance testing specifications, they are illegal as they cannot be tested.
HDMI for long has been considered the industry standard for High Definition content; But Apple's laptops continue to use their own proprietary mini-display ports.
While Apple has tried to muscle its technology to the fore, but it has more or less failed, resulting in many manufacturers developing HDMI to mini-display adaptors.
Notably, HDMI to Mini-Display dongles remain legal as compliance tested HDMI cable can be attached to them.