RIYADH, Saudi Arabia — First lady Melania Trump did not wear a headscarf when she greeted the king of Saudi Arabia on Saturday. Neither did President Trump's daughter, Ivanka, or any of the other women in Trump's delegation.

That's not uncommon, illegal, or even particularly impolite. While Islamic women are required by sharia law to cover their heads while in public, there's no such expectation for western women. And King Salman bin Abdulaziz Al Saud greeted Mrs. Trump warmly at the airport, even directing Saudi customs to shake her hand.

So none of this would be an issue, except for the fact that President Trump himself made it one — when Barack Obama was president.

In 2015, President and Mrs. Obama visited Saudi Arabia to mourn the death of King Salman's brother and predecessor, King Abdullah bin Abdulaziz al Saud. First lady Michelle Obama wore loose, head-to-toe clothing, but did not cover her head.

"Many people are saying it was wonderful that Mrs. Obama refused to wear a scarf in Saudi Arabia, but they were insulted," Trump tweeted. "We have enuf enemies."

Other high profile western visitors — including German Chancellor Angela Merkel, British Prime Minister Theresa May, and first ladies Hillary Clinton and Laura Bush — have also eschewed the headscarf in their visits to the kingdom.

Saudi King Salman and U.S. first lady Michelle Obama hold a receiving line for delegation members at the Erga Palace in Riyadh on Jan. 27, 2015.