Just compensation has been defined as "the full and fair equivalent of the property taken from its owner by the expropriator. The measure is not the taker's gain, but the owner’s loss. The word ‘just’ is used to qualify the meaning of the word ‘compensation’ and to convey thereby the idea that the amount to be tendered for the property to be taken shall be real, substantial, full and ample."¹³ The payment of just compensation for private property taken for public use is guaranteed no less by our Constitution and is included in the Bill of Rights.¹⁴ As such, no legislative enactments or executive issuances can prevent the courts from determining whether the right of the property owners to just compensation has been violated. It is a judicial function that cannot "be usurped by any other branch or official of the government."¹⁵ Thus, we have consistently ruled that statutes and executive issuances fixing or providing for the method of computing just compensation are not binding on courts and, at best, are treated as mere guidelines in ascertaining the amount thereof.¹⁶ In National Power Corporation v. Bagui,¹⁷ where the same petitioner also invoked the provisions of Section 3A of RA No. 6395, we held that:

Moreover, Section 3A-(b) of R.A. No. 6395, as amended, is not binding on the Court. It has been repeatedly emphasized that the determination of just compensation in eminent domain cases is a judicial function and that any valuation for just compensation laid down in the statutes may serve only as a guiding principle or one of the factors in determining just compensation but it may not substitute the court’s own judgment as to what amount should be awarded and how to arrive at such amount.¹⁸