put one on honor
put one on one's honor
Fig. to inform one that one is trusted to act honorably, legally, and fairly without supervision. I'll put you on your honor when I have to leave the room during the test. They put us on our honor to take no more than we had paid for.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.