Questions on Plagiarism include not only how to respond to clear, and not so clear, instances of it, but also how to structure a course so as to minimize its occurrence.
Questions on Codes of Conduct (Honor Codes) may be appropriate here if they focus on students appropriating the work of others. Suggested responses to plagiarism can include both punishment and the teaching of appropriate lessons.
Self-Plagiarism is also appropriate here for situations in which students re-use older work without attribution.