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 was appointed as a lawyer in the Parlement at Poitiers by Queen Mary in 1579, following the publication of his first book on religious and imperial matters. He also claimed to have visited Queen Mary in England according to his biography (1589).