Legislators and other public policy makers have an ethical obligation to develop fair and equitable policy that promotes the health and wellbeing of ALL it's citizens.
They are obligated to create policies that support the right of children to grow up as healthy as possible, to become educated to the the extent of their capacity, to establish families and have children if they choose and to work and be productive.
All of that is to say to compete on a level field in a capitalistic society.
They have special obligations to those who are "lesser situated" as a former colleague, Don Reynolds used to say to protect their interests even when they cannot compete.
With regard to Medicine, I believe their duties and obligations, i.e., thiose of legislators, are limited to assuring that those who practice medicine (in the generic sense) are properly trained, maintain competence, are of good character and act within the accepted professional standards of good practice.
This has all become very confused in that professional associations have given much more attention to the interests of their members, especially income, than they have to developing and promoting "standards" of practice and upholding the integrity of their professions and therapeutic relationships.
Physicians, once the most powerful professionals/people in our society, have stood on the sidelines and been neutered by people all too willing to usurp their power and authority for personal gain -- usually economic gain.
-- Myra Christopher, Kathleen Foley Chair for Pain and Palliative Care, Center for Practical Bioethics