Lol, who told you this?
Depends on how you look at GMOs, in a way all life on this planet is gmo, but taking in account a very precise process of manipulating genes(which is actual "GMO" label) done in labs, I suspect no cannabis plant is gmo yet.
But it has potential to be a useful practice also in canna plants.
BC Buds claims to be raising GMO plants, and I suspect a couple others are. As there is no regulation to the canna seed industry, who knows what some of these people are selling. If you are suspect about any particular strain, I'd write to the breeder and ask.