If you invoke a law, you state that you are taking a particular action because that law allows or tells you to.

If you invoke something such as a principle, a saying, or a famous person, you refer to them in order to support your argument.

If something such as a piece of music invokes a feeling or an image, it causes someone to have the feeling or to see the image. Many people consider this use to be incorrect.

If someone invokes a god, they ask the god for help or forgiveness.