As per case facts... An importer furnished bank guarantees to secure differential customs duty, which the department encashed after the High Court dismissed the importer's challenge to the duty calculation. ... The Supreme Court later allowed the importer's appeal, holding the duty claim was unlawful. The importer then sought a refund, but the department insisted on compliance with the 'unjust enrichment' provisions of Section 27 of the Customs Act. The High Court upheld the department's view, leading to the importer's appeal. The question arose whether the forced encashment of a bank guarantee furnished as court-ordered security constituted 'duty paid' under Section 27 of the Customs Act, thereby attracting the doctrine of unjust enrichment and requiring the importer to prove the burden wasn't passed on. Finally... The Supreme Court allowed the appeal, holding that the encashment of a bank guarantee furnished as security, after the duty claim was determined to be unlawful, does not constitute 'duty paid' under Section 27. Therefore, the doctrine of unjust enrichment was inapplicable, and the department was directed to immediately refund the unlawfully retained amounts with 6% interest.