Discretion

All public functionaries, while performing their duties and exercising discretion vested in them by law, were required to perform such duties and exercise such discretion in a judicious & transparent manner – Any discretion with malafide on the part of public functionary will render all orders passed and proceedings so conducted as illegal and of no legal effect.
Muhammad Amin Chapal  Vs.  Karachi Cantt. Board.
PLD 2012 Sindh 1 (D.B)

-    Fair and transparent discretion – principles - discretionary power conferred on government should be exercised reasonably and subject to existence of essential conditions, required for exercise of such powers within the scope of law. All judicial, quasi-judicial and administrative authorities while exercising mandatory or discretionary jurisdiction must follow the rule of fair exercise of power in a reasonable manner and must ensure dispensation of justice in the spirit of law.

-    Seven instruments/principles
    (i) open plans, (ii) open policy statement, (iii) open rules, (iv) open findings, (v) open reason, (vi) open precedents, (vii) fair informal procedure.

    Power to exercise discretion would not authorize such authorities to arbitrarily, discriminately, and malafide. They have to act without ulterior motive.

    Discretion is to be exercised according to rational reasons which means that; (a) there be finding of primary facts based on good evidence and (b) decisions about facts be made for reasons which serve the purposes of statute in an intelligible and reasonable manner. Actions which doe not meet these threshold equipments are considered arbitrary and misuse of power.
Tariq Aziz ud Din  In Re. Numan Rights Case
2010 SCMR 1301
Also see AIR 1991 SC 101
1997(7) SCC 622 (State of Gujrat)
PLD 1991 SC 14
PLD 2001 SC 1
2006 SCMR 1876
2009 SCMR 1354