States Rights vs Federal Power

We talk about the tension between states rights and federal power. How does a court decide which to lean more heavily on? 

Articles referenced:

Valor

The myth of ‘open borders’

For additional description of how state laws impacted the travel and work of African-Americans or freed slaves in the years before the Civil War, see e.g., Kate Masur, Until Justice Be Done, America's First Civil Rights Movement From the Revolution to Reconstruction, (N.Y.: W. W. Norton & Company, 2021), 123-126 and 157-59).