President Donald Trump’s decision to end an Obama-era policy protecting undocumented immigrants who arrived in the United States as children has sparked immediate blowback in Silicon Valley, where the industry’s two most valuable companies—Apple and Alphabet—were both co-founded by the children of immigrants, and where foreign talent has helped turn the Bay Area into the greatest wealth-generation machine in the world. Tech leaders had already been at odds with the White House over the president’s executive order banning immigration from Muslim-majority countries earlier this year, as well as the administration’s plans to curtail legal immigration including the H-1B visa program. On Tuesday morning, Attorney General Jeff Sessions officially broke the news that Trump would be rescinding Deferred Action for Childhood Arrivals (DACA) in six months, unless Congress passes a law, putting nearly 800,000 so-called “Dreamers” at risk of deportation.

“This is a sad day for our country. The decision to end DACA is not just wrong. It is particularly cruel to offer young people the American Dream, encourage them to come out of the shadows and trust our government, and then punish them for it,” Facebook C.E.O. Mark Zuckerberg, who spent time last week defending DACA by responding to anti-immigration commenters on his Facebook page, said in a statement. “The young people covered by DACA are our friends and neighbors. They contribute to our communities and to the economy. I’ve gotten to know some Dreamers over the past few years, and I’ve always been impressed by their strength and sense of purpose. They don’t deserve to live in fear.”

Zuckerberg was joined by a number of other tech leaders in denouncing Trump’s decision.

Google C.E.O. Sundar Pichai:

Box C.E.O. Aaron Levie, who earlier this year called Trump’s immigration ban “dangerous”:

Facebook C.O.O. Sheryl Sandberg:

Y Combinator’s Sam Altman:

Airbnb co-founders Brian Chesky, Joe Gebbia, and Nate Blecharczyk:

Lyft co-founders John Zimmer and Logan Green:

YouTube C.E.O. Susan Wojcicki:

Uber, which previously offered legal aid for drivers affected by Trump’s travel ban, said that Dreamers “make America more competitive and they deserve the opportunity to work, study, and pursue the American dream.” New C.E.O. Dara Khosrowshahi‏ also tweeted a statement:

IBM released a statement:

In calling for Congress to focus on finding a legislative fix to protect Dreamers, tech companies are effectively prioritizing the immigration issue over tax reform, a decision that Microsoft president Brad Smith made explicit in his own note slamming the DACA decision. “The administration has given Congress six months to replace DACA with new legislation. We believe this means that Congress now needs to reprioritize the fall legislative calendar and move quickly with new legislation to protect these 800,000 Dreamers. This means that Congress should adopt legislation on DACA before it tries to adopt a tax reform bill. This is the only way, given the number of legislative days Congress has scheduled over the next six months, we realistically can expect Congress to complete DACA legislation in time,” he wrote Tuesday. “We say this even though Microsoft, like many other companies, cares greatly about modernizing the tax system and making it fairer and more competitive. But we need to put the humanitarian needs of these 800,000 people on the legislative calendar before a tax bill.”

Uber C.T.O. Thuan Pham, himself an immigrant, wrote a blog post on Tuesday with a personal story about his journey as a migrant leaving Vietnam. “We’ll continue to stand by immigrants who want nothing more than to contribute to our country and pursue the American Dream,” Pham wrote. In a memo to employees, Apple C.E.O. Tim Cook expressed his disdain for the Trump administration’s decision. “I am deeply dismayed that 800,000 Americans—including more than 250 of our Apple coworkers—may soon find themselves cast out of the only country they've ever called home,” Cook said in an e-mail obtained by Axios. “I want to assure you that Apple will work with members of Congress from both parties to advocate for a legislative solution that provides permanent protections for all the Dreamers in our country.”