Which US constitutional principle is primarily challenged when a President deploys a state’s National Guard without the Governor’s consent?

💡 Explanation:

The US National Guard is a dual state-federal entity, primarily commanded by the state Governor. The conflict over the President 'federalizing' and deploying a state's Guard without gubernatorial consent directly challenges the division of powers between the federal and state governments, which is the definition of Federalism (often argued under the Tenth Amendment). When federalized (Title 10 status), the President may deploy them without the governor's consent, but this is a point of contention regarding state sovereignty for domestic law enforcement purposes.