Ethics, Morality, Politics, and Law

Ethics, morality, politics, and law; how are these topics distinct?

Very simply:
Ethics is the science of morality, and politics is the science of law.

To help explain the distinction between the terms, let me first give an example the reader should be familiar with:

Medicine:
Medicine is the science which discovers health. Health is not the same for everyone, but its principles are. For example, it may be healthy for you to take two iron tablets a day, but unhealthy for someone else to. Medicine has no power other than telling you what you ought to do if you wish to achieve health.

Ethics:
Ethics is the science which discovers morality. Morality is not the same for everyone, but its principles are. For example, it may be moral for you to quit your job, but immoral for someone else to. Ethics has no power other than telling you what you ought to do if you wish to achieve good mental health.

Politics:
Politics [in the philosophical sense] the science which discovers law. Law must be the same for everyone and is not subjective (in the sense the above two are.) Law has power in that it will tell you what you must not do within the sphere of all interpersonal interaction. Law, which encompasses rights and property, is the framework on which civil human interactions (i.e. societies) are formed. Law is not government. Law is not arbitrary. The primary purpose of law is to ban the use of arbitrary force in society.

(I do not consider statutes to be law. They are dictates produced by thugs, like orders from a mafia don. Law is what judges and courts produce in practicing the science of politics, much as health is what doctors and hospitals produce in practicing the science of medicine.)

To recap: ethics dictates what you should do, if you wish to lead a moral life, and politics dictates what you must not do, if men are to live together in a civil society.