To hold or esp to profit from two contrary positions; work both sides of the street •Usu in the negative: Make up your mind which one you'll support, because you can't have it both ways(1914+)
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with have it both ways
Achieve two mutually exclusive objectives, as in Bill wants to have it both ways—to enjoy Christmas at home and to travel with his friends. The related
have it all means “to get everything one wants,” as in It's too bad we can't have it all—the wisdom of experience and the fresh enthusiasm of youth.
[ Early 1900s