As persons interested in developing your ethical reasoning abilities, you should be able to differentiate not only ethics and social conventions but also ethics and the law. What is illegal may be ethically justified. What is ethically obligatory may be illegal. What is unethical may be legal.
Laws often emerge out of social conventions. Whatever is acceptable and expected in social groups becomes the foundation for many laws. But, because we cannot assume that social conventions are ethical, we cannot assume that human laws are ethical. What is more, laws are ultimately made by politicians whose primary motivation is often power, vested interest, or expediency. One should not be surprised, then, when politicians are not sensitive to ethical principles or confuse ethical principles with social values or taboos.