Raymond McCord outside the Royal Courts of Justice in Belfast.
Anti-Brexit protesters are seen outside the Houses of Parliament in London. Critics said the PM is shutting down Parliament to stifle debate, and to allow the clock to run down to the UK's scheduled departure from the European Union on October 31.
"We are spending the money on doing lots of things to mitigate those assumptions", he told the BBC.
"He said to date there certainly hasn't been ". any proposal that comes close to doing what the backstop does" submitted to Brussels.
But the moves would be temporary as an agreement on keeping the border open would be a prerequisite to any talks on a trade deal between Britain and the EU. It also says a no-deal exit could trigger major protests and even riots.
Opposition lawmakers and rebel Conservatives have dealt the government's Brexit plans a series of blows.
On Wednesday, Johnson's government also released its "Operation Yellowhammer" Brexit planning document, under duress.
A separate legal challenge to the suspension, brought by British campaigner Gina Miller, will also be heard by the Supreme Court on Tuesday.
Northern Ireland's Lord Chief Justice Sir Declan Morgan, who led the panel, said he had been informed by Supreme Court judge Lord Kerr that the UK's highest court only meant to hear arguments on the prorogation of Parliament next week.
The Government rejected that contention during two days of legal proceedings in the High Court. The stated motivation for the shutdown was to be able to introduce a new domestic legislative agenda with a new parliamentary session.
He said he had "absolutely not" misled the queen - whose formal approval was needed to suspend Parliament - about his motives.
It is the insurance policy to avoid a hard border between Northern Ireland and the Republic of Ireland after Brexit, unless and until another solution is found.
An open border is crucial to the regional economy and underpins the peace process that ended decades of sectarian violence in Northern Ireland.
"We have three judges sitting there and there's no politics in their mindset".
"Virtually all of the assembled evidence belongs to the world of politics, both national and supra-national".
Thursday's ruling paves the way for a showdown in the UK Supreme Court next week - where it is due to hear appeals on the Scottish case as well as the English challenge filed by prominent anti-Brexit campaigner Gina Miller.
He has said he hoped a deal could be reached and that he has an "abundance of proposals" to replace the backstop - but has not detailed what they might be.
Johnson's envoy David Frost has been holding talks in Brussels this week but no breakthrough has been made, and the European Union says it is still waiting for firm proposals from the United Kingdom.
Mr Sassoli was speaking at a press conference after a meeting of the EU Conference of Presidents with EU chief Brexit negotiator Michel Barnier.