It is significant because at her nomination, the American Bar Association said she did not have enough experience to be a federal judge. Since becoming a lawyer, she has not tried a case, civil or criminal, as lead or co-counsel. She had some federal clerkships, spent 10 months at a law firm and three years as a government lawyer.
Charles, you might want to read the following to get a better understanding of the judge. You will discover, for instance, that she has tried cases on behalf of the government, including prosecuting "the largest sex-trafficking case in the history of the Eastern District of Virginia."
https://www.nationalreview.com/news/meet-kathryn-kimball-mizelle-the-judge-who-overturned-the-transportation-mask-mandate/She was confirmed by a vote of 49-41. It is not a question of "authority," but a matter of her general competence as a judge, an indicator of whether her ruling could stand or be easily overturned.
I spent some time reading through her ruling. I'm not sure I agree with her interpretation of the statute at hand. However, she is correct when she says that the Biden Administration did not follow proper APA procedures and, according to SCOTUS when Trump tried to rescind DACA, that's enough.
BTW, stories about this also noted that judges appointed by Democrats have at times used the same reasoning as she did in their rulings, although it is relatively rare that a district judge acts so broadly.
I'm not sure what they mean by "reasoning." While I'm not sure that I disagree with her view of the regulation at hand, I will give her credit for going through it in meticulous detail and spelling out her reasoning.
However, I can think of many times when district judges struck down Trump administration regulations on a nationwide basis--many of them were in Hawaii and San Francisco.
This brings us the related matter of how much authority a district judge should have. While I think she is right in that the Biden Admin violated the APA in making this regulation, I'm not sure I think a lower court judge should be able to strike it down nationwide. OTOH, I'm not sure if its feasible for the regulation to be in effect in some places or for some people when dealing with a nationwide industry. She deals with that issue in her ruling.
While the Biden Administration is going to appeal the ruling, the fact that it is not asking for a stay of the ruling and that the President has said that he thinks masking should be up to the people it's more a matter of principle than the actual regulation.
You might also be interested in this artlcle:
https://www.city-journal.org/the-failed-covid-policy-of-mask-mandatesThe graphs are interesting. There was almost no difference between the 11 states without mask mandates and the 39 that had them.