More honoured in the breach than in the observance
This is usually thought to mean a rule which is more often broken than observed. The context of the play shows the real meaning as 'it is more honourable to breach than to observe'.
From Shakespeare's Hamlet, 1602:
HAMLET Ay, marry, is't:
But to my mind, though I am native here
And to the manner born, it is a custom
More honour'd in the breach than the observance.
See other phrases and sayings from Shakespeare.