warn away from
warn (one) away (from someone or something)
To caution one to leave or not to come near someone or something. The first noun or pronoun can also come after "away." Police had to warn people away from the wild bear, as they kept wanting to get close enough to take a photo. The government put up a sign warning away any potential hikers. My parents tied to warn me away from him, but I just found him too irresistible.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
warn someone away from someone or something
to advise someone to avoid someone or something. We warned her away from the danger, but she did not heed our warning. Why didn't you warn me away from Roger?
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.