When you have a copyrighted work, others must request and receive your permission to use said creation. This should be done formally and may require them to pay you a fee. Here is how to write Cease and Desist Letters to stop copyright infringement.
"First Cease and Desist Demand Letter"
If you notice that someone else has copied your registered, copyrighted work, then you must make sure you document the transgression. Keep the original and a copy of the infringing publication for your records. Write a Cease and Desist Demand Letter to the offending party using your official individual or company letterhead.
Your tone should be official and non-accusatory using the first letter to notify the offender of the transgression. You might not know if the action was accidental or willful. You can use words similar to - "It has come to our attention or we have noticed a copy described as belonging to you that is similar to our work."
Clearly articulate that this was an "unauthorized copy or use of my copyrighted work." The offending party neither requested, nor received permission or authorization to use your work.
"State Your Legal Rights"
State your ownership of the copyrighted work, publication date and registration number. When you have your copyright registered with the United States Patent and Trademark Office (USPTO), you have the right to ask the court to establish an injunction against offending parties. State that your copyright is protected under 17 United States Code Section 101.
Now that all of your facts have been laid out, make your demand that the recipient "cease and desist from all publication, use and distribution of my work." The offender should destroy all physical and electronic copies immediately. You could include a form that the offender could sign and send back to you as verification.
Finally, discuss what could happen if the offender does not cease. If the offending party does not cease and desist, legal remedies could include an injunction, equitable relief, along with court costs and attorney fees under Section 504(c)(2).
"Second Cease and Desist Demand Letter"
If the offending party does not immediately cease and desist, you could have your attorney send the next letter. The second letter could be more accusatory. Having "notified" the offender of your copyright, and the offender continued to commit the crime, this constitutes the willful, intentional infringement of your copyright.