In July 1792 he fought a bloodless duel with the James Maitland, 8th Earl of Lauderdale after the Earl impugned his honor in the House of Lords. With the outbreak of the French Revolution Arnold outfitted a privateer, while continuing to do business in the West Indies, even though the hostilities increased the risk. He was imprisoned by French authorities on Guadeloupe amid accusations of spying for the British, and narrowly eluded hanging by escaping to the blockading British fleet after bribing his guards. He helped organize militia forces on British-held islands, receiving praise from the landowners for his efforts on their behalf. This work, which he hoped would earn him wider respect and a new command, instead earned him and his sons a land grant of in Upper Canada, near present-day Renfrew, Ontario.