The controversy played out across a decade of councils rather than a single ruling. A synod at Diospolis in Palestine in 415 examined Pelagius directly and acquitted him, a verdict that provoked outrage in the West and that Augustine attributed to the bishops there not fully grasping what Pelagius meant. Two African councils at Carthage, in 416 and again in 418, condemned Pelagius and Caelestius by name, and Pope Zosimus, who had initially leaned toward clearing them, reversed course and confirmed the condemnation under pressure from the African bishops and the emperor Honorius, who followed with an imperial rescript banishing Pelagius and his followers from Rome. The Council of Ephesus condemned Pelagianism again in 431, in the same session that also condemned Nestorius.
No reliable source records where Pelagius went after his acquittal at Diospolis or how his life ended; the historical trail simply stops. The controversy outlived him. A mediating position that later theologians called semi-Pelagianism, holding that a person's will can take the first step toward faith which grace then perfects, gained support in Gaul and was itself condemned only later, at the Second Council of Orange in 529, which affirmed a modified Augustinian position as the settled teaching of the Latin church.
Modern historians distinguish Pelagius's own recorded arguments, which are comparatively measured, from the sharper claims of Caelestius and from Augustine's polemical framing of both men as a single, uniform heresy, a simplification the sources themselves do not fully support.