Poland and Lithuania broke European Union free-movement laws by refusing to register right-hand-drive cars purchased in the United Kingdom and Ireland, the European Court of Justice ruled today.

The ECJ said that the ban amounted to discrimination against foreign cars, rejecting claims that right-hand drive cars constituted a safety threat.

The issue came to a head in the aftermath of the financial crisis. As the economies of the UK and Ireland contracted, Poles and Lithuanians moved back to their countries of origin, taking their newly-acquired right-hand drive cars with them.

When Poland and Lithuania refused to register these cars, demanding that their owners convert them into left-hand-drive cars, the owners complained to the European Commission.

In several other cases, dating back as far as 1973, EU courts have told member states that they cannot prevent right-hand-drive cars from being bought and sold throughout the EU.

The ECJ accepted that right-hand-drive cars were more dangerous than left-hand-drive cars in countries where they drive on the right.

Poland and Lithuania have among the highest number of road fatalities per capita in the EU. Poland has 93 road fatalities per one million inhabitants while Lithuania has 100 fatalities. This compares to 28 road fatalities per million inhabitants in the UK and an EU average of 55.

The ECJ ruled that an outright ban on registering right-hand-drive cars was disproportionate.

In particular, the court said that the countries had failed to provide evidence that it was considerably more dangerous to allow right-hand-drive cars. Member states could take other measures, such as requiring owners of right-hand-drive cars to install mirrors to improve visibility.