What makes liberty, which I define as personal autonomy, real in America are two fundamental things:
When one is accused of a crime they are presumed innocent until proven guilty.
Whether one is guilty of a crime needs to be proven by the state beyond a reasonable doubt by a jury of one's peers, or a judge if the accused prefers.
We usually refer to these two items as due process and without it there is no liberty. Further, in our Declaration of Independence we stated that all people, not just U.S. Citizens, are endowed by their creator the right to liberty. Liberty is not provided by the state, it is inherent to who we are as humans. Further, we declared that we create governments for the purposes of preserving these rights.
What are crimes is defined by laws. With the aim of protecting our liberty from individuals and groups who would take it away, which we declared is the purpose of government, our founders created a government that rules by laws, laws written and passed by legislatures made up of people who are voted in to office by citizens to be their representative. This is our form of self government that made America unique in the world at it's founding, and I do not understand how anyone can honestly say the words "Make America Great Again" without accepting and respecting this fundamental tenant.
When one talks about the rule of law they are talking about how people in the United States are ruled. Neither the President nor Congress rule in the United States, the laws are what rule us, and if this rule of law is not respected and upheld by our government the United States of America no longer exists as defined by the U.S. Constitution.
All members of Congress, the President, the Vice President, and Supreme Court Justices take an oath to preserve, protect, and defend the Constitution of the United States. Not respecting, acknowledging or binding oneself to due process and the rule of law is a violation of that oath, which should be an impeachable offense.