*The U.S. Embassy to the Holy See has a Vatican protocol primer that walks people through what is considered the proper dress code.
For men: black or dark suit, aka business attire, with a dark tie.
For women: black skirt or dress that reaches at least the knees, black top with mid- to long-sleeves,
no pants*, simple jewelry, dark closed-toe shoes, and a black hat or veil is optional.
Some blogs and news stories assumed U.S. first lady Michelle Obama wore a long black veil to her July 10 audience with the pope because she was required to do so.
But the Vatican does not mandate that women cover their heads. In fact, the pontifical household said there is no formal or specific dress protocol at all.
Source:
Vatican dress code: Do’s and don’ts for presidential, pilgrim attire, Catholic News Service