The thing with abortion (which for the record I despise) is that it will happen no matter what and enough people think it a right that we cannot justify outlawing it. Murder is obviously less of a gray area for some people (again, I do find it difficult to believe that abortion is considered to be a gray area for anyone, but that is just my personal opinion) and thus would be prevented, as would theft, assault, etc.. There are things we should all (or almost all) be able to agree are unacceptable, and legislate against. Basic rule of thumb is it should be acceptable so long as it does not infringe upon the rights of another in any way. I think going under that basic line of thought a government should be able to operate and grant optimal freedom but still have enough laws in place to keep order.