all's fair in love and war

Meaning

1. in some situations any type of behaviour is acceptable to get what you want

From the same entry

• be fair
• by fair means or foul
• a fair crack of the whip
• fair enough
• fair's fair
• a fair hearing
• a fair shake
• your fair share of
• fair to middling
• it's a fair cop
• fair and square
• set fair