no its not mandatory,apparently only must is....shall is the same as may....so the gun rights may OR may not be infringed....and trumps taxes may or may not be furnished...
"Must" and "shall" mean the same legally....If there is an imperative, the language "is/are required" is used.
So, the use of the word shall is once again an example of the ambiguity of the Constitution, and will be up to the Supreme Court.
Once again Marbury v, Madison will decide the Shall issue, something the singers of the Constitution did not include in COTUS, and its definition will likely be decided 5-4 in Trump's favor.
BTW, Executive Privilege does not exist in COTUS,, nor are Executive Orders.
Odd isn't it that one group of lawyers believe the words must be taken a face value, and others that the document is a living Constitution.