Zeid Raad al-Hussein isn't afraid to speak his mind.

The U.N. high commissioner for human rights has taken on some of the most powerful countries in the world. He has compared populist movements in Europe to the Islamic State, and he called the European Union "inhumane" for its policy of helping the Libyan coast guard intercept and return migrants.

He has suggested that President Trump is a demagogue enabling ethnic nationalism and has denounced his refugee ban as "grossly irresponsible." He has warned that genocide is imminent in Chinese-backed Burma and condemned Russia for its actions in Crimea and Syria.

His fans describe him as brave and tenacious, a strong advocate for human rights at a critical moment.

But it has been a tough battle, one that became even more challenging after Trump's election. Past U.S. administrations have emphasized the importance of human rights, at least rhetorically. Trump, however, has signaled that he is uninterested in prioritizing international norms and commitments, instead advocating for "America First."

Now Hussein is waving the white flag. In an email to his staff, he announced that he will step down after his term ends next summer. He explained that the climate for human rights advocacy had gotten too bad.

"Next year will be the last of my mandate," Hussein wrote in the memo, obtained by Foreign Policy. "After reflection, I have decided not to seek a second four-year term. To do so, in the current geopolitical context, might involve bending a knee in supplication; muting a statement of advocacy; lessening the independence and integrity of my voice — which is your voice."

"There are many months ahead of us: months of struggle, perhaps, and even grief — because although the past year has been arduous for us, it has been appalling for many of the people we serve," he wrote.

The position of high commissioner for human rights was created in 1993. The commissioner is selected directly by the U.N. secretary general. As Mark Leon Goldberg explained at UN Dispatch, that is supposed to protect him from political pressure. The commissioner "is expected to be an independent advocate for human rights around the world," Goldberg wrote. "This often pits the High Commissioner against UN member states."

Hussein's aggressive style, however, ruffled feathers. The New York Times reports that it was unclear for months whether Secretary General António Guterres would support Hussein's second term. (In a statement, Guterres's spokesman said, "The high commissioner has always enjoyed the full support of the secretary general.") The high commissioner has called out every permanent member of the U.N. Security Council.

Hussein's decision has human rights advocates on edge. As Goldberg cautioned:

That he faced this choice at all shows ... that [the] UN human rights system cannot function when the United States so blatantly abandons values-promotion in foreign policy. This does not bode well for the ideal of an empowered UN-backed independent global human rights watchdog defending vulnerable people around the world.