Americans' visa-free access to Europe was on safer ground Tuesday after the EU's top court ruled Brussels need not reciprocate for Washington discriminating against some Europeans visiting the United States.
The European Court of Justice (ECJ) said the European Commission is not automatically required to suspend the visa exemption as it has "political discretion" to decide whether to do so or not.
The ECJ rejected an argument from the European Parliament that the United States barring citizens from a few EU countries from its own visa-waiver programme should automatically trigger EU retaliation.
The commission "cannot be accused of having failed to act", the court said.
The European Union maintains that all citizens from its 27 member countries should be treated equally when they travel outside the bloc.
Currently, the United States waives visa requirements for all EU nationals making short visits of up to 90 days - except for those from Bulgaria, Cyprus and Romania.
Washington previously also required visas from citizens of Croatia, but that country was added to the US visa waiver programme two years ago.
The European Union allows Americans visa-free entry for up to 90 days.
Although EU law upholds a principle that only those outside countries giving visa-free entry to "all nationals of EU member states may benefit from such an exemption for their own nationals" there is no automatic trigger, the ECJ said.
The commission has leeway to decide whether such reciprocity "is justified," it ruled.
Its evaluation needed to take into account the "consequences" of what a reciprocal visa requirement would entail, the ECJ said - a weighty factor, given the United States' trade and economic heft, and close political ties with the EU.
ESTA and ETIAS
For most Europeans, visits to the United States mean obtaining an ESTA - an Electronic System for Travel Authorisation - which acts to screen those eligible for a visa waiver on entry.
The European Union plans to bring in a similar system next year called ETIAS - European Travel Information and Authorisation System - which Americans and other visa-waiver nationalities would need to obtain before boarding.
Both Washington and Brussels say these pre-travel screening approvals do not constitute visas, even though they evaluate applicants against entry criteria, as visas do.
An ESTA application costs $21 (€19.50)and if obtained is generally good for two years. An ETIAS application is expected to cost around €7 and be valid for three years.
Americans last year accounted for five percent of long-haul tourist arrivals in the overall Europe region - which includes the EU and non-EU countries Turkey and Britain - or some 28 million visits, according to the European Travel Commission (ETC), a non-profit organisation that promotes European tourism.
The top destinations for long-haul visitors were Turkey, France, Spain and Britain, the ETC said.