It does appear to be good law that even Federal Court criminal contempts are pardonable by presidents.  (I had  thought there might be a separation of power claim.)

However, the Supreme Curt has hinted, back in 1925, that a pattern of abuse could lead to impeachment.  The language might also provide some tools to persuade the Court to look differently at the Sheriff’s behavior, and any Trump pardon.

Here is what the court said in In the Matter of Philip Grossman, 267 U.S. 87 (1925)

A pardon can only be granted for a contempt fully completed. Neither in this country nor in England can it interfere with the use of coercive measures to enforce a suitor’s right. The detrimental effect of excessive pardons of completed contempts would be in the loss of the deterrent influence upon future contempts. It is of the same character as that of the excessive pardons of other offenses. The difference does not justify our reading criminal contempts out of the pardon clause by departing from its ordinary meaning confirmed by its common law origin and long years of practice and acquiescence.

If it be said that the President, by successive pardons of constantly recurring contempts in particular litigation, might deprive a court of power to enforce its orders in a recalcitrant neighborhood, it is enough to observe that such a course is so improbable as to furnish but little basis for argument. Exceptional cases like this, if to be imagined at all, would suggest a resort to impeachment rather than to a narrow and strained construction of the general powers of the President.
(Bold added.)

There just are not so many Supreme Court cases about impeachment, so every hint is meaningful.  This might stand for:

The proposition that use of pardons, in a pattern, could result in impeachment,

That acts that go to undermining the constitutional balance are appropriate for impeachment,

The idea hat the impeachment clause phrase “high crimes and misdemeanors,” is not necessarily limited to violations of the criminal code.

I would welcome additional suggestions.  Read and enjoy the full case.

More particularly, with respect to Arizona, the use of a pardon to undermine Federal authority is said to be particularly disturbing, for example in a “neighborhood.”   While the Sheriff is now out of power, such a pardon is far more threatening to Federal authority, than an individual violation of the law in the case the Supreme Court decided.

Indeed, a pardon for conviction for systematic abuses of governmental power in breach of the constitution would seem a classic exception requiring rethinking.

A sheriff’s county-wide pattern and practice of contempt for the constitution and the Federal Courts is far more damaging that an ongoing pattern of pardons for minor violations by individuals in a “neighborhood.”  Indeed, given that the case arose under the Prohibition Act, it is understandable that the Court felt the need to recognize that pardons might represent a threat to the enforcement of the law, and therefore hinted at remedies.