The U.S. Constitution separates the branches of the federal government, forcing them to check and balance one another. It also lists and limits the power of Congress, reserving much broader authority for the states to address the concerns of their citizens. Each of these characteristics contributes to a comprehensive structure that is premised on the assumption that we are not angels, and that liberty and prosperity are threatened by any government that vests imperfect humans with unaccountable power.
So, as James Madison wrote, “ambition must be made to counteract ambition.” In an ideal world, Congress, the President, and the states would each guard their own spheres of power, limiting one another and reducing the ability of any one of them to overreach. 
Regrettably, the president has been behaving as though there are no limits to the national government’s power, leaving state attorneys general to assertively take up their role in the process of checking the power and ambition of federal officials.   
Perhaps no specter of unchecked federal authority is greater than the Environmental Protection Agency’s (EPA) ongoing scheme to impose its job-killing Cross-State Air Pollution Rule (CSAPR). The rule unlawfully and unfairly forces states to implement stringent emissions reductions on fossil fuel power plants beyond what they actually contribute to neighboring states. The CSAPR rule would negatively impact electricity prices and reliability for 7 million people in 27 states. In response, we joined with other attorneys general as well as energy companies, trade associations, and labor unions to challenge the validity of this harmful rule. In August, the U.S. Court of Appeals for the D.C. Circuit ruled that the EPA exceeded its statutory authority and struck down the rule.
Eleven state attorneys general also are leading the charge to protect their taxpayers and community banks from the devastating impact of the Dodd-Frank Act, a law that gives the government unprecedented and unchecked power to encourage the cronyism and reckless behavior that caused our financial meltdown in the first place. The Act gives the newly created Financial Stability Oversight Council (FSOC) broad authority to declare any financial firm “too big to fail” and gives another new entity, the Consumer Financial Protection Bureau (CFPB), the power to arbitrarily punish any lender offering loans it deems “unfair.” Exacerbating matters, Congress has no power of the purse or oversight over the CFPB’s $400 million budget, the president cannot remove the CFPB Director except under extremely rare circumstances, and the actions of both the FSOC and CFPB  are subject to limited, if any, judicial review. Such a lack of public accountability cannot stand in a nation that values the rule of law, and it is likely to lead to fewer choices for consumers who seek loans for home purchases, small businesses, or college. 
Oklahoma, Georgia and 25 other states filed suit to stop the Affordable Care Act. Despite the ultimate conclusion that the mandate was justified under the power to tax, the Affordable Care Act decision set important limits on the federal government. The states prevailed on their two main arguments—that the Commerce Clause does not give Congress the power to demand Americans purchase a particular product, and that the Spending Clause cannot be used coercively against the states. Defining these structural limitations on the federal government was an important step toward a more constitutional federal-state balance of power, and attorneys general are continuing to monitor the implementation of the Affordable Care Act. Oklahoma, for example, has challenged the federal government’s unlawful attempt to impose the Act’s taxes on those states whose governors have declined to establish a health insurance exchange pursuant to President Obama’s health care law. 
Admittedly, a discussion about the structural limits on power that are contained within our Constitution may seem dry or old fashioned. But the precipice on which we stand is the direct result of countless decisions made without regard to the most important governing document we share. As the dissenting Justices in the health care case cautioned us:
“It should be the responsibility of the Court to . . . remind our people that the Framers considered structural protections of freedom the most important ones, for which reason they alone were embodied in the original Constitution and not left to later amendment. The fragmentation of power produced by the structure of our Government is central to liberty, and when we destroy it, we place liberty at peril.”
When checks break down and there is imbalance, the vigilance of state attorneys general is the last line of defense against an avoidable consequence – A government completely removed from the people it serves. 

Pruitt is attorney general of Oklahoma) and Olens is attorney general of Georgia.