In another one of those strange and unprecedented moments of the Trump years, the president of the United States showed up at the supreme court the other day. No other presidents have done so, probably because they – to varying degrees – respected the separation of power among the three branches of US government.

But Trump has not shown himself to share in that basic principle.

The high court was hearing a high-profile and immensely consequential case about “birthright citizenship”, and Trump apparently wanted to put his thumb on the scales of justice. A victory for his side would prevent children of undocumented immigrants from automatically becoming American citizens.

He sat there for about an hour, signaling how important this is for his agenda, and hoping, perhaps, that his mere presence would help the cause.

The court seems poised to rule against his position, despite the Trumpian sympathies of some of the most conservative justices.

If so, that ruling will be in keeping with a recent slew of others – mostly at the lower court level – that have not gone Trump’s way.

In recent days, courts have ruled that the president can’t just remake the White House with a hugely expensive ballroom without congressional approval; that an executive order to bar federal funding from public radio and........

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