Principle of Proportionality in Blacklisting — The Court held that the power to blacklist a contractor should be exercised with caution and only in cases where the conduct of the contractor is so deviant or aberrant as to warrant such a punitive measure — A mere breach of contractual obligations without more does not justify blacklisting. B. Guiding Principles for Blacklisting — The Court referred to previous judgments and identified three guiding situations where blacklisting may be justif