President Trump’s pardon of “America’s toughest sheriff,” Joe Arpaio, is reprehensible on many levels, most of which have already elicited due comment. It also has been repeatedly observed that the pardon is “legal,” in the sense that the presidential power to pardon has no explicit limit. Nevertheless, this act by our current president presents an unmistakable, clear and present constitutional danger. It is an attack on our system of government that exceeds any issue in the particular case.

The antidote to autocracy in our constitutional framework is the separation of powers. A truism, often voiced in frustration, is that we have sacrificed efficiency to protect ourselves against concentrated power. This was, in any event, a conscious decision by founders who had rebelled against a king; by and large, it has served us well.

The function of the judiciary in this system cannot be overstated. The first specific enumerated goal in the preamble to the Constitution is “to establish justice.” That reference is preceded only by the general desire “to form a more perfect union.” The remaining goals (promote the general welfare, insure domestic tranquility, secure the blessings of liberty) follow thereafter.

For over two centuries our jurisprudence has been based on the principle enunciated by John Marshall in Marbury v. Madison: Interpretation of the Constitution including, most importantly, invalidating any unconstitutional exercise of power by another branch of government, rests exclusively in the judiciary.

Which brings us to Sheriff Joe Arpaio. A federal district court judge ruled in 2011 that his practice of detaining individuals suspected of illegal immigration solely on the basis of Hispanic appearance violated both the Fourth and Fourteenth amendments. The judge decreed that the sheriff could “…not use Hispanic ancestry as a reason on which to base reasonable suspicion that a crime is being committed” and permanently enjoined Arpaio “from detaining persons based only on the belief that they are in the country without authorization.”

Arpaio stated publicly that he intended to ignore the court’s order, and was as good as his word. In due course and after protracted proceedings, a second federal judge found Arpaio in criminal contempt of the 2011 order. In her decision, the judge characterized him as having “willfully violated” the previous order, and having shown “flagrant disregard” for its requirements. The judge also found that Sheriff Arpaio had ordered his deputies to “continue to detain” suspected illegal immigrants.

The Trump pardon under these circumstances removes the court’s ability to enforce a judicial interpretation of the federal Constitution. Perhaps more than any of the other steps Trump has taken that demonstrate a fundamental disregard for our system of government, this act contains the potential for the greatest and most durable systemic harm.

It is alarming and, in my view, detestable for a law enforcement official to detain individuals based on their Hispanic appearance. Praising that activity from the Oval Office to garner political advantage is in many respects even worse. But the particulars of this case, race and immigration, should not distract us from the fact that we rely on our court system as a balancing force in all cases — not just this one. The judicial system, like any human institution, often performs imperfectly. Here, it carried out its essential function.

Pardons have been abused in the past. They’ve been used to favor former campaign contributors (Marc Rich) and they’ve been politically controversial (Richard Nixon). But they have never before been employed by the executive branch to render dysfunctional a finding of unconstitutional discrimination. The controversial issues underlying Arpaio’s abusive conduct should not distract us from the systemic danger to our constitutional democracy posed by his presidential enabler.