That argument lies at the heart of the "living document" philosopy of Constitutional interpretation - that we should interpret not based on the intent of the original transfer of power, but on what we want it for right now.
The amendment process makes our Constitution a living document, but only to that extent. As George Washington said, the Constitution is a "guide" for each generation of Americans to govern themselves. As the world changes, so does the challenges facing America and her people. Focusing on the growing problems our society has had with illicit drugs in the last 50 years, I believe the Congress and the SCOTUS have acted in a responsible manner consistent with the best interests and welfare of the American people. Again, specific to this case only. Trying to override the Constitutional RKBA, or to find a right of privacy that allows pregnant women to kill their unborn babies in excess of 45 million dead since 1973, I draw the line.