Plagiarism is an ethical issue. Different organizations will have different definitions of acceptable practice. Sometimes plagiarism issues are confused with copyright infringement issues. They are related but different. Copyright is a legal concept controlled by copyright law.
Some people think plagiarism is only an issue in the academic setting. After all, it is not unusual for politicians to use speech writers and the manager of a business group to present group work as his or her own. Here are some articles about plagiarism and its consequences outside the academic community.