I doubt a president could ban carry by him or herself. For example, Bush II supported the AWB but by himself could not ban the guns. But what about those import restrictions?
However, a president could push for legislation to ban and get it through Congress and then it would have to be tested in the courts.
If found unconstitutional, a president could push for an amendment that would allow such.
But this could be done on most of the hot button issues.
If the people go along, then such things would be done.