Federal preemption questions routinely end up decided by narrow Supreme Court majorities

Evidence

Similarly, when states legislate in an area in which congressional legislation exists, litigation often results. For example, in 2011 the U.S. Supreme Court by a 5-4 vote held that a controversial Arizona law penalizing the employment of illegal immigrants was not preempted by federal immigration law. — G. Alan Tarr, Judicial Process and Judicial…, 2783

Categorization

• XREF: Chamber of Commerce v. Whiting (2011) is a key modern preemption case for federalism units. — connects to: Political questions in America routinely become judicial ones — G. Alan Tarr, Judicial Process and Judicial…, 190