Law or not, there's a button for that
I find that for silently taking pictures (of my cat without waking him, for example), the volume button does the same job as the aforementioned "Sound & Display" setting. Yes, either the "Ringer Volume" or the "Silent Mode" checkbox should do the job, but the volume button on the side does even better on the fly (provided that you are not playing media at the time.)
On that note, I've gotten pretty good at hitting pause, volume, and play, depending whether I'm listening to music and trying not to get blasted by ringtones, or trying to not miss a call when my headphones aren't on.
Hope this helps.
-FF on G1 DMD64, Cupcake 1.6