US judges would do well to learn from how the UK’s courts have chipped away at executive prerogative.Donald Trump left his worst offences against American democracy and the US presidency almost until the end of his single term in office, when he refused to recognise his opponent’s election victory and summoned a mob to storm the Capitol. But his final acts—amply availing himself of the presidential pardon power—were nearly as egregious. Gleefully doling out executive clemency to more than 140 people in the last 12 hours of his presidency—including to Steve Bannon, his former chief strategist turned con man—Trump, thwarted in his effort to overturn the election result, clearly revelled in this last kingly prerogative.

It is curious that presidents possess such unaccountable power at all. America’s founders rejected absolute monarchy and its trappings (such as noble titles), and yet the pardon power is descended from just such a monarchical power, the royal prerogative of mercy.

In its original form, this prerogative gave British monarchs the near-unchecked authority to pardon those convicted of crimes. Much like the presidential pardon, it did not fully exculpate the guilty by erasing their conviction, but it did save them from its worst effects—most often a death sentence. In theory, the prerogative was a benign tool to remedy injustice and highlight royal benevolence; in reality, it was always ripe for abuse.

Given that America’s founders understood this danger, their refusal to place more effective checks on the executive looks naive. They trusted that giving Congress the power to impeach the president would serve as 'a great security,' as James Monroe put it. But Monroe wasn’t reckoning on senators being in thrall to a demagogue or binding themselves to tribal partisan loyalties, as the overwhelming majority of Republicans did in Trump’s two impeachment trials.

To align the pardon power with its original purpose, Americans should consider how the United Kingdom’s courts have slowly chipped away at the executive’s use of most, if not all, of the royal prerogative powers by subjecting them to ever-greater judicial scrutiny.

In the 1980s, the House of Lords (whose judicial functions were transferred to the newly established UK Supreme Court in 2009) found that simply because a government minister was relying upon a prerogative power did not make it 'for that reason only ... immune from judicial review,' and held that it was up to the courts to decide if the power could be reviewed. But the courts were wary of asserting too much authority, and in cases where the power related to 'high policy,' affecting matters like foreign affairs or armed conflict, they were usually slow to intervene.

Yet, in recent decades, the UK judiciary has become increasingly unwilling to allow governments to ride roughshod and scrutiny-free over core democratic principles by proclaiming 'high policy.' In fact, the UK Supreme Court’s decision in a seminal 2019 Brexit case, Cherry/Miller (No.2), demonstrates that little remains of the inviolable prerogative.

In that case, the Court was asked if Prime Minister Boris Johnson’s proposed long prorogation (suspension) of Parliament, which was clearly aimed at bringing about a form of Brexit that MPs would not endorse, was lawful. Regardless of the fact that calling and dismissing Parliament is an archetypal prerogative power, the justices unanimously ruled that because the prorogation frustrated Parliament’s ability to 'carry out its constitutional functions as a legislature and ... [supervise] the executive,' it exceeded the 'lawful limits of the power.'

Even as UK courts have whittled away at the scope of the prerogative, ruling on previously untouchable matters, British governments have sought to acquire new unchecked powers. It is now common for legislation to authorise ministers to 'amend, repeal, or replace' parts of the statute, or related statutes, if doing so suits the legislation’s overall purpose or the government’s broader objectives. Moreover, such provisions are often coupled with clauses that attempt to limit, or 'oust,' the judiciary’s ability to review decisions made by ministers wielding these powers.

This lust for power reached its current peak last autumn in the Johnson government’s proposed Internal Market Bill, which concerned domestic regulation after Brexit. Although many members of the government had extolled Brexit as an opportunity to restore Parliament’s 'sovereignty,' the bill sought to bypass the legislature entirely, instead giving ministers the power to rule by decree. It also sought to prevent judicial review of any decisions made by ministers under the statute, while permitting them to make decisions that violated human rights, and, infamously, international law.

Fortunately, the bill’s most odious provisions were eventually dropped before it became law, not least because of then-US President-elect Joe Biden’s strenuous objections. But the outcry the legislation generated has not deterred Johnson from continuing along the same path. In its draft legislation to repeal the Fixed-Term Parliaments Act, for example, the government once more has included an ouster clause, telling the courts that calling elections is a matter for politicians, not judges.

The Johnson government’s resentment of judicial scrutiny is understandable, given its tendency to return bloodied and bruised from its encounters with the courts. But in a liberal democracy, a government that continually loses in the courts must stop behaving unlawfully, not strip away the judiciary’s power.

But behaving lawfully is something that Johnson, like Trump, seems loath to do. The government’s Independent Review of Administrative Law, which is due to release its report this week, was clearly concerned with how Parliament could limit judicial scrutiny. Likewise, the terms of reference of the Independent Human Rights Act Review show a government obsessed with whether human rights interfere with executive ambition.

The US Supreme Court—whose conservative justices tend to espouse adherence to the founders’ 'original intent'—would do well to learn from the UK judiciary’s readiness to innovate in the face of a monarchically inclined executive. In particular, the UK Supreme Court’s willingness to recognise the spirit and purpose of constitutional principles while still applying a coherent and consistent interpretation of the law enhances its ability to respond to novel challenges.

Trump’s blatant violation of the original intent of the presidential pardon was just one of many challenges he posed to the political system established by the US Constitution. Johnson displays similarly worrying traits. Faced with such threats, courts and legislatures need to recall their true purpose: preventing the unchecked exercise of executive power.

—Project Syndicate