Copyright infringement and plagiarism are two different issues. Copyright is a federal law that protects original works from being copied and distributed without the author’s permission unless one of the exceptions applies. Plagiarism is passing off someone else’s work as one’s own or lack of attribution. There is no federal or state plagiarism law but there can certainly be severe repercussions for plagiarizing.
Copyright infringement example: Incorporating an entire poem by Maya Angelou into a published work without her permission. The poem is property attributed to Ms. Angelou.
Plagiarism example: Using a line or even an entire poem by Maya Angelou in a paper and not attributing the poem to the author or citing the source. It would appear that the poem is the creation of the person writing the paper and not Maya Angelou.
For more information on plagiarism, see Purdue’s Online Writing Lab at http://owl.english.purdue.edu