The Sugar Act of 1764 and the Stamp Act of 1765 severely curtailed mercantile trade in the colonies. The Stamp Act prompted Arnold to join the chorus of voices in opposition, and also led to his joining the Sons of Liberty, a secret organization which advocated resistance to those and other restrictive Parliamentary measures. Arnold initially took no part in any public demonstrations but, like many merchants, continued to do business openly in defiance of the Parliamentary Acts, which legally amounted to smuggling. He also faced financial ruin, falling £16,000 in debt with creditors spreading rumors of his insolvency, to the point where he took legal action against them. On the night of 28 January 1767, he and members of his crew roughed up a man suspected of attempting to inform authorities of Arnold's smuggling. He was convicted of disorderly conduct and fined the relatively small amount of 50 shillings; publicity of the case and widespread sympathy for his views probably contributed to the light sentence.