Not a member of any police, but it seems like common sense to me. While you can do it, whos to say its a good idea? I can shove my black lab in the kitchen closet, but that doesnt mean its a good idea to let him live in there until he gets "big enough." Big dogs need room to run, and big fish need room to swim. Its not rocket science. Its responsible ownership. The difference between a happy tang and discontent one is obvious to anyone whos viewed them in both a large public aquarium and a tiny cramped one. Their behavior changes. Simple as that.
To the last poster, I find it sad and irresposible that you advocate continually buying and selling fish to cram into your display.