From The New-York Times October 9, 1861:
THE REBELLION.
… From the Toronto papers we receive particulars of the arrest of Col. RANKIN, member or the Provincial Parliament, for enlisting recruits for the American Army. The offence urged against Col. RANKIN in the complainant’s affidavit is, that he has agreed to accept a military commission to enter into the service of the United Slates, and that he has induced divers of the Queen’s lieges to enlist in the same service. This offence is said to be in violation of the Canadian statute known as “The Foreign Enlistment Act.” In answer to a gross, vulgar attack on Col. RANKIN in the Toronto Leader, that gentleman has thought proper to publish a reply, in which he maintains that, under British law, he and his associates have “a perfect right to enrol themselves in the cause of freedom — that of the North against the South.” And he further says that “there will be no lack of Canadian gentlemen not only willing but eager to avail themselves of the opportunity now presented to them of achieving an honorable distinction.” From the success of Col. RANKIN in filling up his regiment with Canadian recruits, this statement would seem to be literally true. …
Canadian Colonel Arthur Rankin led an adventurous life, which included a role fighting against Northern U.S. citizens during 1838’s Battle of Windsor.
From Windsor’s Scottish Heritage:
In 1861 he [Rankin] returned to Essex to regain his parliamentary seat. But before the session opened, he embarked upon another bizarre international adventure: In July of that year he volunteered to raise a lancer regiment to serve in the Union army in the American Civil War. After discussing the issue with President Lincoln, he was commissioned with a warrant to raise the regiment, with the understanding that most of the men would be Canadians. Canadians, however, were aghast that a militia colonel – he had been promoted commander of the 9th Military District in 1856 – and a Member of Parliament would serve in the American army, and, moreover, would recruit Canadians for enlistment in a foreign army. In October Rankin was arrested in Toronto for breaching the Foreign Enlistment Act, and although he was never convicted, he was forced to resign his American commission. His lancer regiment never saw action and was disbanded in 1862.
You can see the recruiting poster for Rankin’s Lancers at Library and Archives Canada