 Blackwood became a practicing lawyer in the "Parlement" at Poitiers, an appointment in the gift of Mary, awarded in 1579 after the publication of his first polemic, the "De Conjunctione Religionis et Imperii".According to his "Histoire" (1589), Blackwood visited Mary in England.Blackwood's major work was a critique of George Buchanan's dialogue "De Iure Regni apud Scotos", (1579), in which Buchanan had intended to justify to the forced abdication of Mary, Queen of Scots.