Maol Íosa helped to keep the Kingdom of Scotland stable after the death of King Alexander II, and in an example of his behaviour, he is recorded a levying the tenants of the land belonging to Inchaffray Abbey to help preserve the peace.
His marriage into the Comyn family put him very much in the House of Balliol camp during the Great Cause, and in fact Maol Íosa was the auditor of John Balliol at the gathering of Norham. Maol Íosa promised allegiance to King Edward I of England at Stirling in 1292, but rebelled against him along with John Balliol in 1296, and again later during the revolt of Andrew de Moravia and William Wallace. On both occasions, Edward I forgave him, partly one supposes because initially Maol Íosa helped Edward, turning over the rebellious leader of Clann MacDuib.
After the Rising of Robert de Brus, Maol Íosa attempted steer a middle course, but the English king did not trust him, and he was in English custody until 1310. After his release, Maol Íosa remained loyal to the English King (now Edward II), and assisted the English defence of Perth in 1313. He was captured by his son, Maol Íosa IV.
His son obviously persuaded King Robert to spare the father's life, but Maol Íosa nevertheless died in 1317.