One of the big dangers in genetic modification is the tendency to create a strain for a specific set of parameters, the consequence being that a plant may lose some of it's natural ability to mutate, which it would need to survive changes to the ecosystem.
Many of the new modified strains that are planted out in open fields are not as capable if surviving sweeping environmental changes as their non-modified cousins.
Even in cannabis, By growing indoors, we have control of the ecosystem in the grow space, and any genetic changes that are experimented with are not going to run the risk of contaminating the natural ecosystem.