WASHINGTON (AP) — To cover up or not to cover up? Melania Trump wore a veil to the Vatican on Wednesday to meet the pope, but not to an earlier meeting with the king of Saudi Arabia.

Why the difference? The answer is a mix of personal preference, diplomatic protocol and religious dictates.

Vatican protocol says women meeting the pope must wear long sleeves, formal black clothing and a veil to cover their head — rules that aren't strictly enforced. Many women show up to meet the pope without covering their heads. Mrs. Trump is Catholic.

In Saudi Arabia, most Western women don't cover up the way Saudi women and female residents do.

Mrs. Trump also didn't visit any Saudi Muslim holy sites or mosques, where head coverings would have been required.