Five years ago, Oklahoma Attorney General Scott Pruitt, now President Donald Trump's nominee for administrator of the Environmental Protection Agency, sat in the front row as the U.S. Supreme Court debated the contentious Affordable Care Act.

He was part of a coalition of Republican attorneys general fighting President Barack Obama's health law - better known as Obamacare - based on a core party principle: that states' rights trump federal powers, and that programs like Obamacare represent a radical overreach by the federal government.

Now, as Trump looks to undo Obama's legacy and begin constructing his own, Pruitt and other administration Republicans are showing little interest in protecting states' rights. Instead, they are embracing sweeping new environmental, healthcare and immigration policies that are to be imposed on all states.

At the same time Democrats, who over the last half-century have zealously defended sacrosanct federal laws - such as the Civil Rights Act of 1964 that tackled segregation - against arguments that states should be allowed to chart their own way, are now making plans to employ some of those very states' rights positions to fend off Trump administration policies they disagree with.