Saudi Arabia's King Salman greeted then-President Obama as he arrived with then-first lady Michelle Obama in Saudi Arabia in January 2015. The president cut short a trip to India to pay his respects after the death of King Abdullah. (Reuters)

Barack Obama was in Riyadh on Tuesday to pay his respects to the late Saudi King Abdullah. His visit, for which he cut short a much-hyped trip to India, underscores how important the U.S.-Saudi relationship remains to the American leadership. On social media, however, much of the attention has focused on something else: His wife's attire.

As noted by the Associated Press, Michelle Obama did not wear a headscarf or veil Tuesday. In Saudi Arabia, that's unusual: The country is one of the few on Earth where women are expected to cover their heads, and many Saudi women wear niqabs.

[Related: How Michelle Obama made a bold political statement in Saudi Arabia]

Exceptions are made for foreigners, however, and Michelle – who did wear loose clothing that fully covered her arms – appears to have been one of them. In photographs from the official events, other foreign female guests are also shown not wearing headscarves. In the past, Saudi leaders have met with a number of other foreign females without headscarves in the past.

More than 1,500 tweets using the hashtag #ميشيل_أوباما_سفور (roughly, #Michelle_Obama_unveiled) were sent Tuesday, many of which criticized the first lady. Some users pointed out that on a recent trip to Indonesia, Michelle had worn a headscarf. Why not in Saudi Arabia?

The response wasn't entirely negative – Ahram Online notes that some Twitter users said Michelle shouldn't be criticized too much, it being a short, impromptu trip and all. Saudi state television did show images of Michelle and her uncovered head, despite some claims that they had digitally obscured her (a widely circulated video with the first lady entirely blurred seems to have been an amateur production).

Still, the Obamas' trip to Saudi Arabia comes at a time of remarkable international criticism of Saudi Arabia's human rights record, prompted largely by the flogging of blogger Raif Badawi for insulting Islam. The trip was apparently designed to be apolitical – Obama has said he was "unlikely" to discuss Badawi's case with the new Saudi king.

But in Saudi Arabia, the simple act of not covering your head can be political, intentionally or not.

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