Ala. Code § 11-81-224
If the circuit court shall enter a judgment validating and confirming the issuance of the obligations and no appeal shall be taken within the time prescribed by the Alabama Rules of Appellate Procedure; or, if an appeal is taken, the judgment validating such obligations shall be affirmed by the Supreme Court; or, if the circuit court shall render a judgment refusing to validate and confirm the issuance of the obligations and on appeal such judgment shall be reversed by the Supreme Court (in which case the Supreme Court shall issue its mandate to the circuit court requiring it to enter a judgment validating and confirming the issuance of the obligations), the judgment of the circuit court validating and confirming the issuance of the obligations shall be forever conclusive as to the validity of such obligations against the unit issuing them and against all taxpayers and citizens of each organizing subdivision, and the validity of such obligations or of the taxes, revenues or other means provided for their payment and of any pledge, covenant or provision for the benefit of said obligations, to the extent that the validity of any such pledge, covenant or provision shall have been presented to the court and validated by its judgment, shall never be called in question in any court in this state.
Ala. Code § 11-81-224 (1975)