In a landmark ruling that has sent ripples across the Atlantic, the Supreme Court of the United States has handed President Donald Trump a significant expansion of executive authority, even as it delivered partial defeats on specific policies. British constitutional scholars, long accustomed to a system of parliamentary sovereignty and unwritten conventions, are now sounding the alarm over what they see as a dangerous concentration of power in the American presidency.
The court’s decision, released on Monday, centred on the scope of presidential immunity from criminal prosecution for official acts. By a 6-3 majority, the justices ruled that former presidents enjoy absolute immunity for core constitutional functions, a move that effectively shields Trump from prosecution over key actions during his tenure. While the court also ruled that Trump can be prosecuted for private conduct, the net effect of the ruling is a broader shield for executive power than any predecessor has enjoyed.
For markets, the immediate reaction was muted. The S&P 500 edged up 0.2 per cent, but gilt yields in London barely flinched. Yet the long-term implications for capital flows and fiscal credibility are far from benign. Professor Alistair Finch of the London School of Economics described the ruling as ‘a structural shift in the American constitutional order that weakens the checks and balances investors rely upon’. He added, ‘The U.S. risk premium may need to be repriced, especially if future presidents test the boundaries of immunity without fear of legal consequences.’
The ruling comes at a time when the U.S. fiscal deficit is already running at 6 per cent of GDP, and the national debt has surpassed $35 trillion. Bond vigilantes, who have been relatively quiet, may now have another reason to demand higher yields as compensation for political risk. A more powerful presidency, unfettered by legal constraints, could lead to more erratic policy-making, from trade tariffs to fiscal spending. Sterling holders should take note: if American exceptionalism is eroded by constitutional drift, the dollar’s safe-haven status could face a gradual but meaningful challenge.
British constitutional scholars are particularly exercised by the ruling’s implications for the separation of powers. In the UK, the executive is accountable to Parliament, and the courts have limited ability to review prerogative powers. But the U.S. model has always been a cornerstone of liberal democracy globally. ‘This ruling erodes the very principle that no man is above the law,’ said Dr. Emma Whitmore of Oxford. ‘It creates a two-tier system of justice: one for presidents, one for everyone else. That is profoundly destabilising for democratic governance.’
The alarm from British academics is not just theoretical. Investors are beginning to price in the possibility that U.S. institutions are no longer as robust as once believed. Anecdotal reports from City of London brokers suggest a rising interest in German Bunds and Japanese government bonds as hedges against U.S. constitutional risk. Capital is patient, but it is also cowardly, and any hint of political instability in the world’s largest economy will see it flee to the exits.
Of course, the immediate market impact may be limited. The U.S. economy remains the engine of global growth, and the dollar still dominates reserve holdings. But the trend is clear: the post-war constitutional order, which underpinned decades of stability and investment, is fraying. Central bankers on both sides of the Atlantic will be watching closely. If the Federal Reserve is forced to factor in greater political uncertainty, monetary policy could become even more cautious.
For now, the ruling is a reminder that even the most established democracies are not immune to the accumulation of executive power. The City of London will be recalibrating its risk models, and British constitutional scholars will be looking across the pond with unease. The bottom line is simple: when the rules change, so do the returns.
