We can worry about setting precedents later. Congress, the MSM, university professors, and the rest of the elites can discuss it ad nauseum after lives are saved and order established.
Someone earlier in the thread asked that you state how this concept you support would be limited, and you did not directly respond. How about fed action to forcibly close abortion mills? (But it does sound tempting.) Some religious organizations don't believe in blood transfusions, perhaps the army should come in and close the doors of such religious practitioners. It would almost certainly save lives. How about federal intervention on our highways to slow down traffic? Sure, some of these may sound silly to you, but how do we define the paramater for ignoring state officials and substituting federal agencies? This is a very thorny problem, even in the face of what APPREARS to have been a tardy federal response.
You can set up all the what-ifs you want and make all kinds of linkages to other issues. The bottom line is that there is an ongoing crisis of historic proportions involving millions of Americans. Sometimes people have to make hard and immediate decisions based on the circumstances. Saving lives trumps bureaucratic red tape.
I am sorry. Decisions have consequences. In this instance, the decisions were made by the mayor and governor of NOLA. Don't blame the feds for not doing that which they are not allowed to do.