It's not illegal to take steroids (in the UK at least). They are regularly prescribed by doctors for physical rehab and other things. All steroids do in essence is boost the amount of testosterone in your body, while others are there just to stop negative side effects. Nothing wrong with supplements, other than increased kidney function.
Whether he was blatant about it or not is irrelevant. You don't just take steroids and get buff. You still have to eat right and go to the gym religiously to look like he did, granted genetics helped him a lot. Doing it without steroid would have taken longer, he would have still have to do the rest and probably work harder (more risk to his heart).
A lot of athletes take steroids at some point, as well as HGH, there have also been a lot who have had heart attacks (two this year that I know about in football) due to underlying heart defects that were not previously known about.