There are advantages and disadvantages to both approaches. Yes, meditation is legal, and yes there is some control over the meditation experience (though how much control varies from person to person.. some people do seem to have negative experiences and have meditation bring up material they are not ready to deal with, especially without a guide).

On the other hand, most people agree that to get serious results from meditation you have to put in a lot of effort and practice it for a relatively long time. For many people that amount of effort and dedication is unrealistic, especially if all they have to go on to believe that it will eventually pay off is somebody else's word.

Psychedelics, on the other hand, provide virtually instant results. They are also relatively easily available to anyone, requiring almost no effort and no dedication to a long-term regimen of practice. There's no free lunch, however, and so psychedelics do come with their own risks -- risks that can be mitigated to a great extent by thorough preparation, having an experienced sitter, having the proper mind set, etc. But the risks can not be eliminated altogether.

Further, while a psychedelic experience can be profound, it is usually short-lived unless the insights gained during the experience are integrated constructively and put in to practice somehow in one's life -- something most people are not trained to do or even realizing they could/should be doing. A long term meditative practice, on the other hand, will almost by definition have long-term effects.

Another potential benefit of psychedelics is that the access they provide to non-ordinary states of consciousness and mystical experience, and the very real questions they pose about the nature of reality could ignite in the prepared mind a need to seek and perhaps to be open to trying things like meditation. They could also give a glimpse of what could finally be attained through long, hard practice, and some even continue to use psychedelics to enhance their meditative or spiritual practices.

I know in my own case, my experience with psychedelics ignited a life-long, deep interest in philosophy, religion, meditation, other means of attaining altered states of consciousness, and in what lies beyond the appearance of reality. Would I have gotten interested in those things otherwise? Possibly, but I doubt they would have been as important to me had I not had the glimpses of other worlds and other possibilities that psychedelics provided. I know I am far from the only on in feeling this way. I've heard many others credit their psychedelic experiences in similar ways.

From meditation I've learned to deal better with stress, to relax more, and not to get caught up so much in my emotions. Those are great skills to have, but not even remotely close to a psychedelic experience. Some long-time practitioners have reported "enlightenment" or "kensho" experiences with meditation, but there's no guarantee you'll ever have one, and not likely that it'll happen without a ton of practice (some say many lifetime's worth). Even then, those types of experiences in meditation are considered merely another step on the path, a very, very long path.

All in all, this is a complicated subject, without clear cut answers regarding which approach is "better".