Why Trump was correct to issue the Pardon.

Regardless of what you thought of Joe or his tactics Trump was correct IMHO to issue the pardon.

A bit of past history:
What started this was a class action suit for all Latino motorists in Maricopa County. A federal judge in Phoenix entered a preliminary injunction against Arpaio and the sheriff’s office, noting that

“states do not have the inherent authority to enforce the civil provisions of federal immigration law.”

This elludes to illegal entry in the US as a civil provision which is true and false. Being in the US illegally is a civil crime (eg legal VISA that expired), the the act of illegal entry is criminal. (See Title 8, Section 1325 of the U.S. Code (U.S.C.), or Section 275 of the Immigration and Nationality Act (I.N.A.) http://www.alllaw.com/articles/nolo/us-immigration/crime-enter-illegally.html

The Judge ordered Arpaio to stop detaining anyone not suspected of a state or federal crime — simply being in the U.S. illegally is not a crime, only a civil violation which of course is not correct.

This progressed over the next few years and two federal judges found that Arpaio wasn't abiding by the injunction. This brought us current when Judge Susan R. Bolton heard the case herself without a jury. Arpaio had requested a jury trial and was denied by the Judge (an appeal was pending before SCOTUS).

Arpaio had been under intense scrutiny for years under Obama's administration and Eric Holder (head of the DOJ).

The first problem is the judge is trying to say that local Arizona LEOs are not authorized to enforce federal immigration.
However the Congressional Research Service "Authority of State and Local Police to Enforce Federal Immigration Law" says differently. https://fas.org/sgp/crs/homesec/R41423.pdf

One whole section of this document is called "Express Authorization for State and Local Officers to Enforce Federal Immigration Law" and as you can tell by the title specifically says that local law enforement officers are most clearly permissible to enforce federal immigration law. It also clearly says that states do have the ability to over rule these federal immigration laws.

So to recap many of the troubling things about this case.

1. How does a federal judge come to the conclusion that a law enforcement officer does not have the duty to enforce federal law?
2. A judge denied Arpaio's right to a Jury trial and was clearly biased and had found him guilty before the trial even started.
3. If liberal judges and political leaders dislike our current immigration laws, they should use our legislative system to change the law. They won’t do that because they know most Americans do not support open borders and it's easier to target enforcement officers instead via the bench even when they clearly ignore Federal Law themselves.
4. The conviction was clearly the culmination of a political witch hunt by the Obama administration to sideline and destroy Trump as well as inhibit immigration law enforcement.
5. Trump issued the pardon as a big F-U (because he can) to the Obama administration for targeting a law enforcement officer in a witch hunt with the help of several liberal judges that clearly violated the law, while allowing Hillary Clinton to walk free with so many crimes against our national security.

Of course the liberal media is going nuts over this but let's all keep this in perspective. Arpaio was convicted of a misdemeanor.
Compare this to any of Obama's pardons and it's not even objectionable. How about comparing to Bradley/Chelsea Manning or Oscar Lopez Rivera?

Army Pvt. Bradley/Chelsea Manning pardoned after seven years of what was supposed to be a 35-year sentence for passing secret documents to WikiLeaks that violated several federal statutes and was a major concern for National Security.

Oscar Lopez Rivera Lopez headed a Chicago-based cell of the Armed Forces of National Liberation (FALN), which waged a futile but violent struggle to win Puerto Rican independence. FALN claimed responsibility for more than 120 bombings between 1974 and 1983 in a wave of senseless destruction that killed six and injured dozens. In 1981, a federal court in Chicago sentenced Lopez Rivera, then 37, to 55 years for seditious conspiracy, armed robbery, interstate transportation of firearms and conspiracy to transport explosives with intent to destroy government property.