I'm assuming you're referring to Trump saying he has 'total authority' in regards to re-opening the country?
I don't find the statement that was made by him to be fully true myself (my opinion), but I also think it could be interpreted different ways depending on the context of the actual statement that was made and of course what particular laws he is basing that statement on. Of course, with the media, no matter what Trump says, they'll argue against him and find some way to point out that he's 'wrong' because of their bias against him.
In regards to who has the authority to re-open the country, I've seen a few news articles today that say that the 10th amendment gives the states authority to re-open the country and that the president does not have a national authority to do so.
Now IMO, the tenth amendment "The powers not delegated to the United States by the Constitution, nor prohibited by it to the States, are reserved to the States respectively, or to the people." was clearly put in place to LIMIT federal power from over-reaching. How I interpret the 10th is basically in modern language "We've already laid out the freedoms and rights of the people in this Constitution, but just in case some bozo tyrant shows up and tries to say something otherwise (that we haven't thought of nor mentioned), he doesn't have the power to override this; the power goes right back to the people." I believe the 10th amendment was put in place to make sure that power could not be centralized and rather the power was distributed among the people as much as possible.
With that being said, look at what's been taken from us in the last few weeks in regards to our freedom. And look at how many laws and executive orders have been signed in the last decade that take more and more away from us. I'm sure both sides could argue well based on what's been penned in paper way back when and what's been penned in paper recently.
Rather than my own interpretation, I would really like to know Sharkey's thoughts on this.