Could there be a law on stolen bitcoins? What if there would be a law punishing those who steal bitcoins and those people behind scam sites? And if so, is it necessary to have such law? I'm just wondering, if there would be such law about stolen bitcoins, it could be a big relief to us bitcoin users. But then, there are so many questions and issues that goes with this ideal that makes me skeptical about it.

Yes it could, but it would only apply to certain countries. Because I think not all the countries would agree to it, and some may just don't care about it.
And I believe that it's pretty necessary to have that kind of law, but the thing is I don't like if the government interfered with Bitcoin. Because Bitcoin shouldn't be governed by them.