I read from a CNBC news article how Michigan’s attorney general said Trump has a “legal responsibility,” under state law, to wear a mask as a precaution when visiting factories. Trump refuses to wear a mask despite federal health guidance saying he should. I know it is a state law that says the president should wear a mask, but is there a way with the United States' legal framework that the Michigan's attorney general could bring some kind of legal action against the President for breaking Michigan's state law?
I don't know how that would end, but states' AGs have take action against Trump personally in other matters, and that's bubbling through the courts; latest news I found on something like that on quick search (May 15):
A lawsuit accusing President Donald Trump of illegally profiting off the presidency through his luxury Washington hotel was revived Thursday by a divided federal appeals court. [...]
Maryland Attorney General Brian Frosh and District Attorney General Karl Racine — both Democrats — said they hoped Thursday's ruling from the 4th U.S. Circuit Court of Appeals in Richmond would jumpstart efforts by the two jurisdictions to obtain financial records showing how much state and foreign governments have paid the Trump Organization to stay at the hotel and hold events there. More than three dozen subpoenas issued to various government agencies were put on hold while Trump's appeal was pending.
The lawsuit was filed almost three years ago. U.S. District Judge Peter Messitte refused to dismiss it, but his ruling was overturned in July by a three-judge panel of the 4th Circuit. The judges found that Maryland and the District of Columbia lacked standing to pursue their claims against the president.
But on Thursday, the panel's ruling was overturned by the full court of 15 judges. In a 9-6 ruling, the court found that the three-judge panel overstepped its authority when it ordered Messitte to dismiss the lawsuit.
"We recognize that the President is no ordinary petitioner, and we accord him great deference as the head of the Executive branch. But Congress and the Supreme Court have severely limited our ability to grant the extraordinary relief the President seeks," Judge Diana Gribbon Motz wrote for the majority in rejecting Trump's request to dismiss the lawsuit. All nine of the judges in the majority were nominated by Democratic presidents.
The six judges who disagreed — all nominated by Republican presidents, including three by Trump — wrote a scathing dissenting opinion, saying the lawsuit should be thrown out.
"The majority is using a wholly novel and nakedly political cause of action to pave the path for a litigative assault upon this and future Presidents and for an ascendant judicial supervisory role over Presidential action," Judge J. Harvie Wilkinson III wrote.
DOJ spokeswoman Brianna Herlihy said the department is disappointed in the ruling.
POTUS is not generally above the law, even the law of a state that he is visiting. The main question here is whether there was a clear violation of the law, and if so, what could be done about it. The claim that there is a violation of the law rests on this executive order. Before getting into the details of the order, there is a standard legal question as to the legality of an executive order, in particular, what powers are granted to the governor in the case of a declared emergency. The order is advanced under the theory that since, statutorily, "the governor may promulgate reasonable orders, rules, and regulations as he or she considers necessary to protect life and property or to bring the emergency situation within the affected area under control", the particular orders are legal. There are challenges to these orders, and it is not patently obvious whether this authority will be upheld. There is at least a colorable claim that the order is legally invalid (I'm not giving odds on that outcome, I'm saying that this is a factor regarding the "can take legal action" question).
The order requires that "Any individual who leaves their home or place of residence must wear a face covering over their nose and mouth..." with a list of circumstances. It would be a stretch (one always stretches when dealing with the law) to deem that Trump had not left his home or place of residence or that he had done so outside of Michigan jurisdiction. Then we have to assume some facts that constitute the violating circumstance, for example "When in any indoor public space". I don't know the evidence surrounding the alleged violation in Michigan factories, but an obvious question to ask is whether it constitutes a "public space". Grocery stores are, because they are open to the public; most factories are not open to the public. The order explicitly makes an exception limiting "public space" to exclude child care centers and day, residential, travel, or troop camps, which are places normally open to the public. There are exceptions to the mask requirement, the most imaginable being "Are communicating with someone who is hearing impaired or otherwise disabled and where the ability to see the mouth is essential to communication" and "Are giving a speech for broadcast or an audience".
a violation of a penal law of this state that is not a felony or a violation of an order, rule, or regulation of a state agency that is punishable by imprisonment or a fine that is not a civil fine.
so usually a misdemeanor does not include "a violation of an order". But MCL 10.33 specifically overrides this, saying
The violation of any such orders, rules and regulations made in conformity with this act shall be punishable as a misdemeanor, where such order, rule or regulation states that the violation thereof shall constitute a misdemeanor
and the order says "a willful violation of this order is a misdemeanor". The maximum penalty would be a fine of $1,000.
So there is a legal path whereby the Michigan AG could initiate legal proceedings against Trump for not wearing a mask while in Michigan. Then a number of factual and legal questions would no doubt arise. However, they would not arise w.r.t. federal health guidance, because federal health guidance is not legally enforceable in Michigan, or anywhere else.