LESS than a month before the Supreme Court considers the legality of his executive order barring travel from six overwhelmingly Muslim countries, Donald Trump has handed a gift to those challenging the ban. Reacting to a bombing on the London underground on September 15th, Mr Trump first condemned the “loser terrorist” who perpetrated the attack, calling the bomber “sick and demented” and noting that potential miscreants “must be dealt with in a much tougher manner”. Then he brought the issue home: “The travel ban into the United States should be far larger, tougher and more specific—but stupidly, that would not be politically correct!” In dealing with the likes of the Islamic State, he concluded, America “must be proactive & nasty!”

The logic of Mr Trump’s tweets is puzzling: he suggests that political correctness is to blame for the inadequate size, toughness and specificity of his March order, but he, after all, is the president who signed that order, and one of Mr Trump’s campaign pledges was never to kowtow to political correctness. That oddity aside, the tweets feed directly into the narrative of the case against Mr Trump’s ban: that the order “was issued with the improper purpose of banning Muslims” rather than in light of legitimate national-security considerations. Mr Trump’s executive order “uses nationality as a proxy to ban Muslims”, the challengers say, and “ignores the government’s own conclusion that the ban would not advance” America’s interest in protecting itself against attack.

During his presidential campaign, Mr Trump called for “a total and complete shutdown of Muslims entering the United States”, noted his belief that “Islam hates us” and said “we’re having problems with the Muslims, and we’re having problems with Muslims coming into the country”. That may sound rather damning, but some judges have questioned the legal tactic of citing campaign statements in court. In March, Judge Alex Kozinski of the Ninth Circuit Court of Appeals found fault with his colleagues’ position that Mr Trump’s rhetoric as a candidate should come back to haunt him in court. It’s an “evidentiary snark hunt”, he wrote, to thumb through stump-speech transcripts for damning bits. Candidates say “many things on the campaign trail” that might be “contradictory or inflammatory” when “the poor shlub’s only intention is to get elected”. Construing campaign rhetoric as evidence for the motivation behind positions taken as president could unconstitutionally discourage candidates from saying controversial things, Judge Kozinski argued, and should be out of bounds in court.

These are not light worries: if campaign rhetoric becomes fair game for litigation, presidents could spend their terms in office fighting off countless legal challenges, and candidates may feel compelled to parse words. The concerns do not apply, however, to things presidents say after they take the oath of office. Everything a president communicates to the nation is a presidential act, and Mr Trump has been all-too-clear that his tweets represent his true and unfiltered views. With that in mind, Mr Trump’s tweets in response to the bombing in London are revealing and badly undercut his lawyers’ defence of the travel ban as a mere pause to allow the government to examine entry procedures from certain countries.

In his tweets, Mr Trump quite openly admits his preference for a “larger, tougher and more specific” ban than the immigration and refugee pauses he ordered in March (a somewhat softer version of his chaos-inspiring January order, which sank in court and was abandoned by the administration). “Larger” could only mean the prohibition should apply to more countries—presumably a wider, or perhaps total, entry ban on people from Muslim countries. “Tougher” is a tougher adjective to parse, but presumably it means a ban without caveats like those imposed by the Supreme Court in June, when it said Mr Trump’s order could not apply to foreigners with family connections in America. As for “more specific”, one wonders what Mr Trump has in mind. Perhaps the most plausible reading, even without access to his hostility-filled campaign statements, is that Mr Trump would prefer his ban to target Muslims by religion rather than to rope out people based on their residency in predominantly Muslim countries.

When coupled with the insistence that America must be “nasty” in dealing with potential terrorists, another feature of Mr Trump’s morning tweetstorm becomes apparent: his certainty that the bomb was placed by Muslim extremists, long before any suspects were identified or named. That speculation—absent any evidence—is the very definition of prejudice. It will probably be part of the conversation when the Supreme Court hears Trump v International Refugee Assistance Project on October 10th.