The fifth Earl was a Jacobite sympathiser and supported the Earl of Mar in favour of James Stuart, the Old Pretender, in an unsuccessful rebellion in 1715 known as "the Fifteen", or "Lord Mar's Revolt". For his role in the rebellion the Hanoverian government passed a Writ of Attainder for treason against Lord Carnwath in 1716. He was sentenced to death, with his titles and what then remained of the estates being forfeited. The death sentence was later to be remitted by virtue of the Indemnity Act 1717.