Balance of Power has long been a principle in society and government but was most explicit in the Constitution of the United States. The House, the Senate, the President, and Supreme Court, and Sovereign States were supposed to balance each other's avarice and keep their activities within limits by each blocking the other's excesses.
This balance was compromised in 1913 when Amendment 17 provided for direct election of Senators, and the Income Tax and Federal Reserve were passed. This left both the House and Senate responsible to the same urban majority rather than split power between the elected Representatives and the State appointed Senators. The States were left with little influence over their Federal creation. The new tax and money power gave the Federal government unlimited resources to buy votes and reward supporters. Federal programs have grown exponentially ever since.
This result would have been no surprise to the Founders because governments throughout history have grown out-of-control until stopped by failure or violence. Tyrants will slowly expand their overreach hoping that we will not notice and accept their new "settled law".
So who enforces the Constitution when the entire government is cooperating in the excess? Notice that the Supreme Court has become just nine more politicians.
Part of the answer is that every public officer has sworn to uphold the Constitution and must refuse when any government officer exceeds their authority, and defend citizens against abuse. Notice that they are not sworn to obey other government officers or any specific law, but to uphold and defend the Constitution. The elected Sheriffs are part of the balance of power, they are supposed to defy other branches. The same obligation is on every public officer whether in law enforcement or not.
The final answer is ourselves. We also have the obligation to resist. That is the way Liberty works. Those in power push for more power and we push back to assure our freedoms. We must let any government or private power know, that exceeding its authority will be resisted. Gandhi and Martin Luther King showed us that violence need not be used, but that we must suffer the violence of the tyrant as the cost of proving our resolve.
But are we not to obey the law? Of course we obey the laws when they do not violate our rights and are made within the proper authority of the law-making body. That is what "rule of law" means, not only that laws are to be obeyed but that the laws are themselves lawful. When laws exceed authority or violate our rights, then it is our duty to resist. Reread the Declaration if you have forgotten why. Natural Law and Common Law are the laws of the people. Government law, also known as Statutory Law, is the law of the King and requires our vigilance and resistance.
Throughout American history citizens have resisted government abuse. They often acted imprudently but were acknowledged by the public who saw the point of their grievance. Sadly, any reform accomplished is often later circumvented by government as public attention wanes. The government and private appetite for power is never abated, so eternal vigilance is mandatory if our freedom is to be preserved. We are the balance.