Any thought that Silicon Valley might work with President Trump ended when the tech industry took a decisive stand against his Muslim ban. It simply had no other choice.

The condemnation has been swift and nearly unanimous. Today, Google employees worldwide walked off the job to protest the ban; CEO Sundar Pichai and co-founder Sergey Brin came out to support them. Over the weekend, big tech companies, venture capitalists, and even CEOs like Elon Musk and Travis Kalanick who are advising Trump denounced the draconian policy. It was a rare moment of unanimity for Silicon Valley, which is almost by definition a globalized industry built by, and welcoming toward, immigrants. Opposition to Trump's immigration crackdown isn't just political. It's personal.

"No nation is better at harnessing the energies and talents of immigrants," Amazon CEO Jeff Bezos wrote today in a note to employees detailing the company's opposition to the ban. "It’s a distinctive competitive advantage for our country—one we should not weaken."

Many see the ban as an existential threat. Of the 274,000 skilled-worker visas, known as H-1B visas, the US issued in 2013, 60 percent went to people in computer-related jobs. More than that, though, the ban goes to the heart of the Valley's culture, which emphasizes inclusion and globalism. It's the stuff of legend. Steve Jobs was the son of Syrian immigrants, and Brin's parents fled the Soviet Union when he was a child. As he told a reporter during a protest at San Francisco International Airport, "I’m a refugee."

Sabba Nazhand, enterprise sales director at the web-based event planning platform Social Tables, says many people feel the ban personally. Even people who aren't immigrants work alongside them and consider them friends. "It hit home," says Nazhand, who was born in Iran. Whatever the external political considerations of tech companies might be, tech employees have had to come to terms with the reality of the immigration ban in ways that radiate outward, even at big companies.

Tech has clashed with Trump before, but the tensions seemed to ease after the election. Trump accused Amazon of being a monopoly, but Bezos promised to give the president “his most open mind” and even provided him with some positive PR by announcing 100,000 new US jobs in Amazon warehouses. Google quietly shifted its lobbying strategy to court more Republicans. And tech leaders made the trip to Trump Tower in December for a meeting with the president. On any other issue, tech might have chosen to compromise or lobby or push the law to its limits. But not now. Not this.

“(The immigration ban) is the first thing that a business can’t work around,” says Rachel Dobroth, director of operations at Social Tables and Nazhand’s fiancée. That’s a tough reality to face for an industry that has demonstrated skill at getting what it wants from—or in spite of—the government.

Trump’s ban leaves tech companies with a seemingly intractable problem that threatens both their core values and their most crucial resource. "Tech’s fundamental success is firmly rooted in its people," says Husayn Kassai, the 27-year-old Iranian co-founder of the identity verification startup Onfido, who moved to San Francisco eighteen months ago when the company decided to expand to the US. Trump’s order hinders his company's growth. Its headquarters are in London, and Kassai says traveling here would be too precarious .

“The rules changed overnight,” he says. “Who knows whether they could change again?”

When Kassai talks about the impact of the immigration order, he can’t help but also mention his family—many of whom live in London. His brother, his brother’s wife, and their two kids planned to visit Kassai in the Bay Area this spring to celebrate the Iranian New Year. But no longer. And Kassai says that had known Trump had serious plans to ban immigration, he would have considered setting up shop in Canada instead.