Adel Osseiran began his political career in 1936 right after his graduation when, alongside various dignitaries from Southern Lebanon (Jabal Amil), he began to campaign for the abolition of the tax that the French mandatory authorities were levying on agricultural land, particularly on tobacco farmers. After being arrested for making a fiery speech, he was taken to court and assigned a lawyer. However, he rejected all manner of legal counsel and undertook his own defense, turning it into a vigorous and spirited attack on the wrongdoings of the French mandatory authorities, as he saw them.