Do you not feel they have not had ample opportunity to read the Meta section here? There are multiple threads weekly on this very subject. It takes all of 2 seconds for them to click the Meta button and read a few of the thread titles and see what is not acceptable here.
Not having read the rules is a very shallow excuse by the way. Plagiarism is frowned upon in every area: school, work etc.
Copying works of others is a universal issue, and it is worse if the motive behind it is for personal gain (financial or acknowledgement)
For clarity a welcome message could be added for new members and this could include the rules and guidelines and a few other vital posts.