Day by day, week by week, courts are increasingly becoming the front line in the struggle to preserve democracy from populists and authoritarians. In the United States, the Supreme Court recently heard oral arguments on a decision by Colorado's highest court that Donald Trump is ineligible to appear on the state's presidential ballot, owing to his role in the January 6, 2021, insurrection at the US Capitol. And an appellate court has ruled against Trump's claim that presidents enjoy immunity for any action taken while in office.

Moreover, a state court in New York has just imposed a $354 million penalty on Trump for financial fraud. That comes on top of $83 million awarded by the jury in a case where Trump was accused of defaming a woman who had successfully sued him for sexual assault. In addition to barring him from holding any senior role in a New York-based company for the next three years, these two rulings will likely strip Trump of almost all his available cash holdings.

Meanwhile, across the Atlantic, the United Kingdom's Conservative government has been trying to pass a migrant-relocation bill that is intended to bypass a UK Supreme Court ruling late last year overturning similar legislation. In Israel, the country's highest court recently struck down an amendment to the Basic Law that would have curtailed its own authority. And in Germany, the Constitutional Court recently ruled that public funding can be denied to the far-right, anti-democratic Die Heimat party, leading to speculation that it could consider a similar case involving the increasingly popular Alternative für Deutschland (AfD).

The ballot-eligibility case before the US Supreme Court may turn out to be one of the most important in US history. After the Colorado Supreme Court ruled that Trump's role in the January 6 insurrection bars him from holding high office, it became inevitable that the top court would have to weigh in.

Having accepted the case, the justices must decide whether they will block Trump's return to the presidency, knowing that he has promised to unleash "bedlam" if they rule against him. But even if Trump's followers cause disorder, America's system of democracy - which was designed to deter demagogues - will have held. By contrast, if the justices overturn the Colorado decision, as seems likely, the future of American democracy may well be left to just a sliver of voters in key swing states.

The courts and the law have been interwoven with American political life almost since the founding. In 1835, Alexis de Tocqueville observed that, "Scarcely any political question arises in the United States that is not resolved, sooner or later, into a judicial question." This was no exaggeration. In 1803, the Supreme Court had asserted, in Marbury v. Madison, its authority to review and, if necessary, strike down legislation, establishing itself as the final arbiter on the meaning and requirements of the US Constitution.

Although America has long been the world's preeminent democracy, few other countries have adopted its judicial model. Within the US, the sovereignty of the Court is taken almost for granted, with only occasional murmurs of dissent. But many observers elsewhere are troubled by the idea that a few men and women in black robes could decide on, say, the creation of a national bank or the legality of slavery. While almost every democratic country has a constitutional court, few are as politically super-charged as America's. Instead, they are expected to defer to elected officials.

And yet, populist politics have increasingly strained many countries' constitutional orders, leading to more instances of courts asserting themselves in novel ways. A good example is the right-wing Israeli administration's attempt to bar the country's Supreme Court from considering "the reasonableness of a decision of the government, the prime minister, or any other minister."

Last month, Israel's Supreme Court struck down that law. Following in the footsteps of their American counterparts, the justices determined that the Court - not the Knesset, not the government, and not the president - is the highest authority on the meaning and requirements of Israel's Basic Laws.

In the UK, where the courts have long been described as "lions under the throne," last year's ruling striking down the government's migrant-relocation law suggests that the justices will come out of the shadows when necessary. The government's attempt to send asylum seekers to Rwanda, the court ruled, amounted to a violation of both international and domestic law, because - contrary to what the Foreign Office claims - Rwanda does not qualify as a safe country for resettlement.

It is unclear what will happen if Prime Minister Rishi Sunak's government manages to pass a bill declaring Rwanda to be "safe," simply because no British government has ever adopted legislation whose sole purpose is to deny reality. (In fact, Rwandans seeking political asylum in the UK already outnumber those whom the UK is trying to send to Rwanda.)

If the UK's traditional conception of parliamentary sovereignty holds, the Supreme Court will be obliged to accept this Alice in Wonderland outcome. Still, even if the justices prove unwilling to topple the constitutional apple cart in this particular case, the broader shift in judicial power is clear, both in Britain and internationally.

To survive this period of populist assaults on the democratic order, courts will need to embrace their proper role as arbiters of justice. They know that their decisions cannot rest on the emotional whims of a Trump or a Boris Johnson. They must follow reason, precedent, and law.

At a time of mounting populist pressure, the judiciary's apparent democratic unaccountability will likely prove to be one of its fundamental strengths, not a weakness. They may now be the last guarantors of democratic constitutional order.

From Project Syndicate