Fair And Square Meaning

(idiomatic) Within the applicable rules.

Example:   We won the game fair and square
1885, Marietta Holley, Sweet Cicely; or, Josiah Allen as a politician, page 177:
  He said they give licenses now to steal — steal folks'es senses away, and then they would steal every thing else, and murder, and tear round into every kind of wickedness. But he didn't ask that. He wanted things done fair and square: he jest wanted to steal horses. He was goin' West, and he thought he could do a good business, and lay up something. If he had a license, he shouldn't be afraid of bein' shot up, or shot.
1976 Oct 28, Charlie Waters quoting S. I. Hayakawa, “First biennial Harold Stassen Awards”, The Prescott Courier:
  For the "Most Accurate Assessment of an International Situation" the unanimous winner is the Republican U.S. Senate hopeful from California, S.E. Hayakawa. He said, "Of course we should keep the Panama Canal, we stole it fair and square."