The UK Government's controversial blueprint for post-Brexit Britain is being debated this week.

The Internal Market Bill has been widely condemned for disrespecting international law by overriding the Withdrawal Agreement and acting as a "Trojan horse" to destroy devolution. But why?

What is the UK internal market?

When the Union between England, Wales and Scotland was created, the internal market ensured there was "open and unhindered trade" across the UK's four nations.

When the UK joined the then-European Economic Community in 1973, most of the British trade laws were replaced by European laws.

The devolution of powers to Scotland, Wales and Northern Ireland in the 1990s was made within the context of EU membership, so they had power over some policy areas, such as agriculture, but they could not contradict EU law.

What is the purpose of the UK Internal Market Bill?

When the UK joined the then-European Economic Community (EEC) in 1973, most British trade laws were placed by their European counterparts. Devolution of powers to Scotland, Wales and Northern Ireland in the 1990s gave powers over certain policies but could not contradict European law. 

It would eventually come to be known as the Single Market. Regarding all EU member states as one territory, it devised rules about everything from food standards to fisharies to ensure consistancy across the bloc.

Now that the UK is leaving the EU, we will (eventually) leave the Single Market. The Internal Market Bill is its proposed replacement, aiming to ensure all four of the UK's home nations are not limited by regulations determined by each devolved government.

As the four nations will no longer be constrained by EU law, the bill aims to create common rules that apply across the UK - essentially replacing the Single Market with a similar UK-wide framework.

What does the Bill propose?

The bill proposes to bring forward legislation that will enshrine "mutual recognition and non-discrimination".

Mutual recognition is defined in the bill as making sure any goods, services and qualifications which can be sold or used in one part of the UK can also be in another part of the UK, with some exceptions for Northern Ireland as laid out in the protocol.

Non-discrimination laws would make it unlawful for any of the four nations' governments to introduce rules or regulations that would favour goods or services in one part of the UK over another.

There is also a list of precedents the new law would override, including "any other legislation, convention or rule of international or domestic law whatsoever, including any order, judgement or decision of the Europe Court or of any other court or tribunal".

It also promises Edinburgh, Belfast and Cardiff will be given new powers to create their own laws in 160 policy areas once the transition period is over.

Why has it caused controversy? 

The mutual recognition provision could see devolved nations having to accept goods and services from other parts of the UK, even if their governments have set different standards.

It emerged last week that, under section 46 of the Bill, the UK Government would be able to fund projects in Scotland directly if councils applied for cash, even if Holyrood ministers did not approve of the plans.

Under the clause, which is there to replace EU structural funds, Westminster would be able to invest projects in devolved areas such as health, education and road infrastructure.

Read more: 'Trojan horse' trade bill could lead to Scottish NHS and water privatisation

There are fears that food standards could also be affected by the legislation if the UK Government decided to allow products from the US, such as chlorinated chicken and hormone-injected beef, to be sold in England.

It will also override parts of the withdrawal agreement that came into law in January, by allowing free trade between Northern Ireland an the UK without any checks.

What is the Northern Ireland protocol?

A crucial part of the Internal Market Bill, and therefore the Withdrawal Agreement, the Northern Ireland protocol aims to avoid the introduction of a hard border on the island of Ireland in the event of a no-deal Brexit.

It states that Northern Ireland will remain part of the UK's customs territory so, if the UK signs a free trade deal with another country, Northern Irish goods would be included.

However, Northern Ireland will have to stick to some EU rules to allow goods to move freely into the Republic.

Goods moving from the rest of the UK to Northern Ireland will not be subject to a tariff unless they are "at risk" of being moved into the EU afterwards.

It also lead to increased checks on the border with the Republic of Ireland, which the UK and EU previously agreed could not happen.

Will the bill break international law?

Yes, according to the UK Government. Northern Ireland Secretary Brandon Lewis told the House of Commons that "this does break international law" but said only in "a very specific and limited way".

The Bill would essentially override a key part of the withdrawal agreement - article four - which says it takes precedence over UK domestic law.

This, he said, was because the government wants to allow ministers to decide what constitutes state aid in Northern Ireland and what goods arriving in it from Great Britain should be subject to customs checks.

But it could open the country up to a court battle with the bloc - and the head of the UK government’s legal department reportedly quit over the proposals.

Jonathan Jones, the Treasury solicitor and permanent secretary at the Government Legal Department, the sixth senior Whitehall official to resign this year, was said to be "very unhappy" about the decision to overwrite parts of the Northern Ireland protocol. 

And former Attorney General Geoffrey Cox said the Prime Minister is damaging the UK's reputation by pushing it through. 

Mr Cox, Mr Johnson’s former attorney general when the Withdrawal Agreement was signed, said the government “knew” what it was signing up to when it ratified the exit terms.

He said: “What I can say from my perspective is we simply cannot approve or endorse a situation in which we go back on our word, given solemnly not only by the British Government and on behalf of the British Crown, but also by Parliament when we ratified this in February, unless there are extreme circumstances which arrive involving a breach of duty of the good faith by the EU.

“In those circumstances, there are then lawful remedies open to us and it is those we should take rather than violating international law and a solemn treaty.

“The breaking of the law leads ultimately to very long-term and permanent damage to this country’s reputation and it is also a question of honour to me – we signed up, we knew what we were signing.”

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