Five supporters of the European Migrants Forum (EMF) will refuse to show their passports to customs officers at Stansted airport to challenge Britain's insistence on maintaining the checks on travellers from the EU.
The British president of the EMF, Tara Mukherjee, said Britain was acting illegally under article 7a of the Treaty of the European Union by maintaining the internal border controls. The European Commission shares the Forum's view that article 7a, guaranteeing free movement of goods and people within the European single market, means that internal EU border controls should be dropped.
The principle of open borders pre-dates the Maastricht Treaty by six years. The Single European Act, signed in 1985, sought to create freedom of movement for goods, services, capital and people. But there is a continuing dispute over what some of its articles mean, in particular 7a, which prescribed the easing of border controls.
So, at the 1985 Luxembourg summit, heads of state and government agreed that the Single European Act did not affect the rights of member states to take measures to control the movement of immigrants from third countries and to prevent terrorism or crime.
The same year, the so-called Schengen Group of states, which did not include Britain, decided to go ahead with a truly border-free area.
Britain continues to believe that the Luxembourg statement safeguards its right to passport checks at airports and ports, as well as the Waterloo Channel tunnel rail link terminal.
But the European Commission, federalist members of the European Parliament and some civil rights groups have grave doubts. They think Britain must drop these controls as the legal force of the summit statement is open to doubt and Britain does not have an opt-out or a derogation.
The European Parliament has brought a court case against the Commission charging that it has failed to carry out its responsibilities. If the Parliament wins the case in the European Court of Justice, the Commission might be required to demand Britain remove these border checks.
Mr Wardle apparently wanted to put the issue on the agenda of the 1996 Inter-Governmental Conference when the EU meets to rewrite its rules. He has claimed that Home Office legal advice indicates that Britain does not have a leg to stand on, but British officials in Brussels yesterday denied this. Mr Wardle seems to have wanted the Government to demand a cast-iron legal guarantee.
Britain argues that border checks do not impede free movement of EU citizens. And it says that they are necessary to check whether those entering the UK are legally permitted.
All member countries demand passports for people entering their territory from outside the EU. But as most have land borders, they often do not demand passports for those arriving by road or rail. However, they do conduct spot checks inland and, in most countries, citizens are required to carry identity cards. Britain has no such requirement because - apart from in Ireland - it has no land border with another EU state.
Progress in carrying out the Single Act has been slow because much of the accompanying legislation has not yet been agreed.Reuse content