BRUSSELS (Reuters) - British Prime Minister Boris Johnson has made a fresh push to drop the so-called Irish backstop from the Brexit deal, renewing a demand the EU has repeatedly rejected.

Anti-Brexit protesters demonstrate in Westminster, London, Britain, August 20, 2019. REUTERS/Hannah McKay

In a letter to European Council President Donald Tusk, Johnson said that the backstop - an insurance policy to keep the Irish border open after Britain leaves the European Union - was “anti-democratic”, and demanded its removal from the stalled divorce deal.

The backstop would require Britain to obey some EU rules if no other way could be found to keep the land border between British-ruled Northern Ireland and EU member Ireland invisible. Dublin says this is crucial to maintaining peace on the island.

Below is some information about the backstop, the points made by Johnson and the EU’s reaction.

WHAT IT IS

Currently, the border between EU member state Ireland and the UK province of Northern Ireland has no checks or infrastructure, as both are members of the EU and fall under the same ‘single market’ customs and regulatory arrangements.

Brexit will end this - but a new trade deal between the EU and the UK may take years. Even coming up with special arrangements and technology to make checkpoints unnecessary may prove lengthy.

So the backstop envisages that, if all else fails, the UK will remain bound by some EU rules on customs, as well as various production, environment and other standards.

WHY UK HAS A PROBLEM WITH IT

The previous prime minister, Theresa May, approved a Withdrawal Agreement with the backstop in it, but the British parliament struck it down three times.

Under the mechanism, the UK would remain in a customs union with the EU “unless and until” alternative arrangements were found.

But many British pro-Brexit lawmakers argue that this would make Britain a “vassal state”, unable to do its own trade deals around the world and still overseen by EU judges.

WHAT JOHNSON SAID

In his letter, Johnson said the backstop “cannot form part of an agreed Withdrawal Agreement” and must be replaced with a “commitment” to put in place “alternative arrangements” by the end of the post-Brexit transition period.

He said the UK was willing to legally commit not to erect border infrastructure, and hoped the EU would do the same, calling for “flexible and creative” solutions.

He noted that “there will need to be a degree of confidence about what would happen if these arrangements were not all fully in place”, but did not specify what this might mean.

WHY THE EU REJECTS THAT

The EU has long insisted that the delicate Irish issue must be settled swiftly, along with Brexit.

It sees Britain’s refusal to agree to the fallback plan now as only reinforcing the need for an insurance policy.

Despite discussions on “alternative arrangements” between Brussels and London, the EU does not see them as a viable option, at least for now, as the necessary technology is not available yet.

The bloc stresses that London has already agreed to the backstop, and sees Johnson’s letter as an effort to pin the blame for the failure of negotiations on the EU.

Crucially, the EU is worried about Johnson’s ambition, stated in the letter, to distance Britain from the bloc’s rules on the environment, animal and food safety, state aid and labor laws, which he presented as the purpose of Brexit.

LEVEL PLAYING FIELD

Preserving a ‘level playing field’ of customs and regulations after Brexit is crucial to the EU as whatever enters Ireland from Britain has free access to the rest of the bloc’s single market.

Brussels needs to ensure that such products would not undermine agreed common standards, or compete by price dumping.

Without an agreement with Britain, it would insist on checks on the border - which might be a threat to a Northern Ireland peace settlement that depends to some extent on unimpeded north-south movement.

Alternatively, the EU could run checks between Ireland and continental Europe, but that would damage Dublin’s economic interests and subordinate them to non-member Britain’s.

NO-DEAL BREXIT

Johnson promised in his letter that the British government and parliament would swiftly endorse a Brexit deal without a backstop in it. But he also says the UK will leave the EU on Oct. 31 regardless.

While Johnson’s more hawkish stance has made an abrupt split more likely, many in Brussels still doubt that Brexit will materialize this autumn.

They suspect that parliament may block it, or that the process may be held up by a snap British election.