Amidst the tumultuous aftermath of the election of Donald Trump this week, a group of Silicon Valley elite proposed that California should secede. And they’re serious. But how would they actually go about making that happen?

1/ If Trump wins I am announcing and funding a legitimate campaign for California to become its own nation. — Shervin (@shervin) November 9, 2016

The dream of seceding from the union is almost as old as the union of the United States itself. In just the past 30 years, people in Alaska, California, Florida, Georgia, Hawaii, New Hampshire, South Carolina, Texas and Vermont have all led (failed) movements to secede. In the last election, after President Barack Obama was re-elected, more than 125,000 Texans signed a petition asking the federal government to allow the Lone Star State to go solo. But so far in U.S. history, the only successful secession was before the Civil War, when 11 states split off to form the short-lived Confederacy. Northerners maintained that the pull-out from the Union was illegal—a contention that was a large part of why the two sides went to war. And we know how that turned out.

As excited as Trump haters on the West Coast might be about this plan, they should know that the Golden State’s odds of becoming the Independent Republic of California aren’t very good given the legislative process involved. California couldn’t just build a wall tomorrow, stop paying taxes to the federal government, and start requiring passports for “foreigners” from the rest of the U.S. to enter the state. While the Declaration of Independence enshrined the “Right of the People” to “alter or abolish” any form of government that becomes destructive, the Supreme Court has consistently ruled that doesn’t mean a state can just up and leave.

The Supreme Court has consistently ruled that doesn’t mean a state can just up and leave.

In the 1869 Supreme Court case Texas v. White, the Supreme Court found that the Confederacy’s secession had in fact been illegitimate in the eyes of the federal government. The Constitution, the court said, created “an indestructible Union, composed of indestructible states.” In 2006, Justice Antonin Scalia affirmed that this is still the court’s thinking when he was asked by a screenwriter if Maine seceding made any sense as a possible plot point.

“I cannot imagine that such a question could ever reach the Supreme Court,” Scalia wrote in response. “To begin with, the answer is clear… If there was any constitutional issue resolved by the Civil War, it is that there is no right to secede.”

In 1869, though, the court did recognize that some division of the country could happen “through revolution, or through consent of the States.” But while the Constitution specifies exactly how a state can gain admission to the United States, it affords no mechanism by which to leave it. So for California or any state to bid the U.S. bon voyage , it would require an amendment to the Constitution.

California would either have to forcibly and unconstitutionally withdraw from the nation, or get nearly everyone in the U.S. to agree that it’s a good idea.

After Trump’s election to the presidency, Uber investor and Hyperloop One co-founder Shervin Pishevar argued that California, which has the sixth largest economy in the world, should secede and use its economic weight to leverage nationwide changes, like the end of the Electoral College. The Yes California campaign has been arguing for a referendum on California’s secession since long before Trump’s election, citing the economic, cultural and political differences between California and the rest of the nation. “Trump voters might actually approve California becoming its own republic,” Pishevar told me, arguing that the divisive political climate in America might just be crazy enough to be willing to let California flee.

A California assemblymember proposed drafting a bill for secession. https://t.co/UdpKNuyKgj — Inhomogeneous-SIS (@isislovecruft) November 10, 2016

Unfortunately for Pishevar, amending the Constitution is a feat difficult enough that it has happened only 17 times in 227 years. An amendment requires the support of either two-thirds of Congress or two-thirds of states at a constitutional convention, along with ratification by three-quarters of the states. In other words, for California to actually secede, it would either have to forcibly and unconstitutionally withdraw from the nation, or get nearly everyone in the U.S. to agree that letting the world’s six largest economy leave its tax-paying ranks is a good idea.

Just in case anyone cares, I think “Calexit” is beyond dumb. America matters more. It is a very small group, not the POV of “tech.” — John Lilly (@johnolilly) November 10, 2016

There are some scholars out there who argue a Supreme Court ruling from 1869 saying secession is illegal doesn’t settle the matter.

“If in 2065, Alaska, California, Hawaii, or Texas assert a right to secede, the argument that ‘in 1865, the victorious Union government concluded that no state has a right to secede in opposition to the wishes of the Union, so therefore you lack such a right’ will have precisely the weight that the Americans of 2065 will choose to give it — which should be very little,” law professor Eugene Volokh wrote in 2010. “The present is different from the past, and the future from the present.”

Volokh, though, was clear that he was no fan of the idea of secession. He feared the economic and political instability that it would bring, instability that it certainly brought in the past.

“For many Americans in the North and the South, disunion was a nightmare, a tragic cataclysm that would reduce them to the kind of fear and misery that seemed to pervade the rest of the world,” historian Elizabeth R. Varon wrote. “And yet, for many other Americans, disunion served as the main instrument by which they could achieve their political goals.”

When President James Buchanan gave his 1860 State of the Union in the midst of the pre-Civil War secession crisis, his words did seem to invite the possibility of secession. If the North and the South truly could not resolve their differences, he said, the South might be justified in leaving the union.

But Buchanan’s vision of a divided nation was a nightmare, not a dream.

“Our thirty-three States may resolve themselves into as many petty, jarring, and hostile republics, each one retiring from the Union without responsibility whenever any sudden excitement might impel them to such a course,” he said. “By this process a Union might be entirely broken into fragments in a few weeks which cost our forefathers many years of toil, privation, and blood to establish.”