What happens if someone misuses my Creative Commons-licensed work?
A Creative Commons license terminates automatically if someone uses your work contrary to the license terms. This means that, if a person uses your work under a Creative Commons license and they, for example, fail to attribute your work in the manner you specified, then they no longer have the right to continue to use your work. This only applies in relation to the person in breach of the license; it does not apply generally to the other people who use your work under a Creative Commons license and comply with its terms. You have a number of options as to how you can enforce this; you can consider contacting the person and asking them to rectify the situation and/or you can consider consulting a lawyer to act on your behalf. For information about how you may be able to locate a suitably qualified lawyer, please refer to this question and answer.
