User blog comment:Pauldin91/Garp has Haoshoku Haki/@comment-28573618-20160926014816

A lot of people are saying he didn't, but let's not forget the most important detail here. This is a Toei screw-up. Until Oda shows Garp using Haoshoku Haki, it is and will remain unconfirmed.

There's also the question of whether the ability is hereditary, which I think is highly likely. I believe Garp does have it as well as Dragon since Luffy does have it. Haoshoku Haki could simply be something that needs to be awakened through sheer willpower if the family line has it in their blood. Look at how Luffy awakened his each time before he was taught how to control it. This also goes for Roger and Ace since Ace has been confirmed to have Haoshoku Haki and Roger, being the Pirate King and everything he's done, most likely had it.