I believe that Dell, like Charlton, was their own distributor. There's not a lot that I can find online about the history of periodical distribution (it deserves further study, too), but Mark Evanier definitely states here that Dell was the distributor and financier for Western Publishing. When that deal soured and Western began Gold Key, Dell had to fill the pipeline with something, and that's when the mostly atrocious 60's Dell material began appearing.
So not only did Dell pretty much not worry about the CCA because of their material ( I mean, really, the CCA is going to object to material that passes the muster of Hollywood studio licensing requirements?), but since it was a Distributor enforced requirement, they could bypass any questions themselves. In other words, DELL vouched for the material to the regional independent newsstand distributors, and had enough of a reputation to get away with it.