The Swedish government has ramped up the pressure on the Schengen agreement, by reintroducing border controls on the Öresund Bridge between Copenhagen and Malmo.
The controls apply to travellers using trains, buses and ferries to enter Sweden from Denmark.
The action is in response to the numbers of migrants travelling through Denmark to reach Sweden.
There are concerns over the economic impact of the controls, which are increasing commuting times for the 20,000 commuters that use the bridge each day.
For many, this is a major development. The Nordic countries have enjoyed freedom of movement since the introduction of the ‘Nordic Passport Union’ in 1952, predating the EU's Schengen agreement by more than 40 years.
Technically, the checks do not breach the Schengen code, as they are not systematic. However, they do increase pressure on the agreement, particularly in the light of the Danish decision – also this week - to introduce similar procedures on its land border with Germany.