Summary: Constitution of Pakistan, 1973—Arts. 141, 142(a), 142(c), 143, 175F(3), 185(3)—Constitution (Eighteenth Amendment) Act, 2010—Constitution (Twenty-Seventh Amendment) Act, 2025—Excise Duty on Minerals (Labour Welfare) Act, 1967—S. 3—Balochistan Finance Act, 2020—S. 7—Legislative competence—Provincial autonomy—Labour welfare—Excise duty on minerals—Doctrine of pith and substance—Doctrine of double aspect legislation—Cooperative federalism—The Federal Constitutional Court considered whether the amendment made through S. 7 of the Balochistan Finance Act, 2020 to S. 3 of the Excise Duty on Minerals (Labour Welfare) Act, 1967, enhancing the rate of duty on minerals, was beyond the legislative competence of the Provincial Assembly of Balochistan on the ground that duties of excise fall within the exclusive federal domain under Entry 44 of the Federal Legislative List. The Court held that, after the Eighteenth Amendment, legislative power is distributed such that the Federation legislates only on subjects enumerated in the Federal Legislative List, while residual subjects vest exclusively in the Provinces; labour welfare, not being part of the Federal Legislative List, is therefore a provincial subject. The Court further held that the 1967 Act, when read as a whole and especially in light of its preamble, was enacted not merely to impose a fiscal levy, but to finance measures for promoting the welfare of labour employed in the mining industry. Accordingly, although the statutory mechanism employed was the levy and collection of excise duty, the dominant constitutional purpose and essential character of the legislation lay in labour welfare, which squarely fell within provincial competence. The amendment made by the Province was, therefore, not unconstitutional merely because it touched upon a fiscal instrument also known to federal legislative entries. Constitutional law—Doctrine of pith and substance—Incidental encroachment—Validity of legislation—The Court reaffirmed that where legislative spheres appear to overlap, the true nature and character of the impugned law must be determined through the doctrine of pith and substance. A law does not become invalid merely because it incidentally trenches upon a field otherwise assigned to another legislature; only a substantial encroachment disturbing the constitutional distribution of powers may render it ultra vires. Applying that doctrine, the Court held that the impugned provincial amendment did not amount to an impermissible invasion of federal legislative authority, because its real object was to support labour welfare in the mining industry and the enhancement of the levy was only a means adopted to advance that constitutionally legitimate provincial purpose. Constitutional law—Doctrine of double aspect legislation—Same subject viewed from different constitutional aspects—The Court also invoked the doctrine of double aspect legislation and explained that a single subject may, in one aspect and for one purpose, fall within federal competence, and in another aspect and for another purpose, fall within provincial competence. Thus, while the levy of excise duty as a fiscal subject may ordinarily fall within the federal domain, the same measure, when examined from the standpoint of labour welfare and public interest in relation to mine workers, may validly operate within the provincial sphere. In such circumstances, both legislative aspects may co-exist in constitutional harmony, and the Court should prefer an interpretation that sustains rather than destroys legislation enacted by democratically elected bodies. Federalism—Post-Eighteenth Amendment constitutional structure—Cooperative federalism—The Court emphasized that the post-Eighteenth Amendment constitutional arrangement broadens provincial autonomy and reflects a commitment to participatory and cooperative federalism. The Federation and Provinces are not to be viewed as functioning in isolated compartments; rather, constitutional interpretation should favour harmonious operation of their respective powers. A rigid or formalistic reading that disregards the practical interaction of fiscal measures and welfare objectives would be inconsistent with the constitutional design. The impugned amendment, therefore, was held to represent a lawful and harmonious exercise of legislative power in furtherance of a legitimate provincial objective. Case references—Prafulla v. Bank of Commerce (AIR 1947 PC 28); Multiple Access v. McCutcheon (1982 CanLII 55 (SCC)); Sui Northern Gas Pipelines v. S.K. Pvt Limited (2025 SCMR 570); DG Khan Cement v. The Province of Punjab (2014 PTD 478); Pakistan College of Law v. University of the Punjab (W.P. No. 45178 of 2017, Lahore High Court). Petition dismissed—Leave refused—The Federal Constitutional Court held that the amendment introduced by S. 7 of the Balochistan Finance Act, 2020 did not fall outside the legislative competence of the Provincial Assembly of Balochistan. The petition was accordingly dismissed, leave was refused, and no order as to costs was made.