Editing Upper Canada (section)

===1837 Rebellion and Patriot War===
{{Main|Rebellions of 1837–1838|Upper Canada Rebellion|Patriot War}}

Mackenzie, Duncombe, [[John Rolph (politician)|John Rolph]] and 200 supporters fled to [[Navy Island]] in the [[Niagara River]], where they declared themselves the [[Republic of Canada]] on 13 December. They obtained supplies from supporters in the United States, resulting in British reprisals (see [[Caroline affair]]). This incident has been used to establish the principle of "anticipatory self-defense" in international politics, which holds that it may be justified only in cases in which the "necessity of that self-defense is instant, overwhelming, and leaving no choice of means, and no moment for deliberation". This formulation is part of the [[Caroline test|''Caroline'' test]]. The ''Caroline'' affair is also now invoked frequently in the course of the dispute around [[preemptive strike]] (or [[Preemptive war|preemption]] doctrine).

On 13 January 1838, under attack by British armaments, the rebels fled. Mackenzie went to the United States where he was arrested and charged under the [[Neutrality Act of 1794|Neutrality Act]].<ref>{{cite DCB |title=McKenzie, William Lyon |first1=Frederick H. |last1=Armstrong |first2=Ronald J. |last2=Stagg |volume=9 |url=http://www.biographi.ca/en/bio/mackenzie_william_lyon_9E.html}}</ref> The Neutrality Act of 1794 made it illegal for an American to wage war against any country at peace with the United States. Application of the Neutrality Act during the Patriot War led to the largest use of US government military force against its own citizens since the [[Whiskey Rebellion]].<ref>{{cite journal|last=Bonthius|first=Andrew|title=The Patriot War of 1837–1838: Locofocoism with a Gun?|journal=Labour/Le Travail|year=2003|volume=52|issue=2|pages=11–12|doi=10.2307/25149383|jstor=25149383|s2cid=142863197}}</ref>

The extended series of incidents comprising the Patriot War were finally settled by US Secretary of State [[Daniel Webster]] and [[Alexander Baring, 1st Baron Ashburton]], in the course of their negotiations leading to the [[Webster–Ashburton Treaty]] of 1842.