President Corazon Aquino signed Executive Order No. 292, institutionalizing the Administrative Code of 1987 as the fundamental law governing the administrative organization of the Philippine government. This Code superseded the Revised Administrative Code of 1917 and consolidated executive reorganization under the 1987 Constitution.

The Administrative Code of 1987 took full effect on November 23, 1989, two years after its promulgation. The delayed effectivity allowed government agencies time to transition from the 1917 Code and align their operations with the new administrative framework.

The Supreme Court clarified the requirements of administrative due process under the Administrative Code, ruling that notice and opportunity to be heard are essential but formal trial-type proceedings are not always required. The decision established the flexible nature of administrative hearings.

The Supreme Court reinforced the substantial evidence standard for administrative proceedings under the Code, holding that decisions of administrative agencies must be supported by such relevant evidence as a reasonable mind might accept as adequate. This ruling guides judicial review of administrative actions.

The Supreme Court held that administrative decisions become final and executory after the reglementary period for appeal has lapsed, interpreting Section 47 of the Code on finality of administrative orders. The ruling established that final administrative decisions acquire immutability absent grave abuse of discretion.

The Supreme Court reinforced the doctrine of exhaustion of administrative remedies under the Code, holding that parties must first pursue remedies available within administrative agencies before seeking judicial intervention. Exceptions include cases of estoppel, urgency, and questions of law.

The Supreme Court held that the principle of res judicata applies to administrative proceedings under the Code, preventing relitigation of issues already decided by administrative agencies with quasi-judicial powers. The decision strengthened the binding effect of administrative adjudications.

The Supreme Court delineated the concurrent jurisdiction of the Office of the Ombudsman and administrative agencies over disciplinary cases under the Code. The ruling clarified that the Ombudsman's constitutional mandate does not divest agencies of their administrative disciplinary authority under Book V.

The Supreme Court reiterated that substantial evidence—such relevant evidence as a reasonable mind might accept as adequate to support a conclusion—is the quantum of proof required in administrative proceedings under the Code. Courts cannot substitute their judgment for that of administrative agencies on factual findings.

The Supreme Court applied Section 44 of Book I on the presumption of regularity of official acts and validity of public documents issued under the Administrative Code. The ruling reinforced that public officers are presumed to have performed their duties regularly absent clear evidence to the contrary.

The Supreme Court clarified the grounds for administrative liability of government employees under Book V of the Code, distinguishing administrative offenses from criminal acts. The ruling emphasized that administrative cases proceed independently of criminal prosecutions.

The Supreme Court held that administrative agencies can only exercise powers expressly granted to them by law under the Administrative Code, applying the doctrine of delegated powers. Acts beyond an agency's statutory authority are ultra vires and void.

The Supreme Court interpreted Section 51 of Book V on preventive suspension, holding that it is not a penalty but a precautionary measure to prevent the respondent from using position to influence witnesses or tamper with evidence during administrative investigations. The 90-day limit is mandatory.