1
general::
Have the support of fact, justice, or reason. For example, Nancy's parents were in the right when they took her teacher to task, or, as Shakespeare put it in Richard III (5:3): "He was in the right, and so indeed it is." [Late 1400s] Also see the antonym IN THE WRONG.
American Heritage Idioms
2
general::
Phrase(s): in the right
correct; morally or legally correct. • I know I’m in the right. • You are not in the right on this point.
McGrawhill's American Idioms And Phrasal Verbs