"The president said at a news conference that the new program is 'the right thing to do' in light of Congress's failure to pass the administration's proposed revision of the Immigration Act," Scalia, a Reagan appointee, wrote in his dissent. "Perhaps it is, though Arizona may not think so. But to say, as the Court does, that Arizona contradicts federal law by enforcing applications of the Immigration Act that the President declines to enforce boggles the mind."
Actually his own written dissent boggles the mind a lot more:
"Must Arizona's ability to protect its borders yield to the reality that Congress has provided inadequate funding for federal enforcement—or, even worse, to the executive's unwise targeting of that funding?" Scalia asked. Later, he added: "What I do fear—and what Arizona and the States that support it fear—is that 'federal policies' of nonenforcement will leave the States helpless before those evil effects of illegal immigration."
"The federal government "does not want to enforce the immigration laws as written, and leaves the States' borders unprotected against immigrants whom those laws would exclude," Scalia alleged.
Arizona's entire immigration law should be upheld, Scalia wrote, because it is "entitled" to make its own immigration policy. At one point, he cites the fact that before the Civil War, Southern states could exclude free blacks from their borders to support the idea that states should be able to set their own immigration policies."
So by this premise the South was right-slavery should still be the law of the land. And this is the highest court in the land!