The European Union (EU) has backed the UK's policy to introduce plain, standardised packaging for cigarettes across the country.
The European Court of Justice ruled the EU Tobacco Products Directive as lawful, overturning challenges from the tobacco industry.
The court also confirmed that EU member states can go further than the requirements set out in the directive in relation to packaging.
Countries will be able to launch standardised packaging when the directive comes into force on 20 May.
Cancer Research UK tobacco policy manager George Butterworth said: "This court decision tells us what we knew all along - that the Tobacco Products Directive is an effective and proportional set of measures to stop children taking up smoking.
"This will help to lower smoking rates in the UK and protect more people from developing cancer.
"It's truly shameful that the tobacco industry has poured so much time, effort and money trying to undermine it. UK laws can now continue as planned and from 20 May the rollout of plain, standardised packaging begins."
The UK, France and Ireland have already passed legislation on standardised packaging and the new European Court of Justice ruling will support other member states who plan to proceed with the measure.
The court also dismissed other legal challenges claiming regulations on e-cigarettes were disproportionate and the ban on menthol flavouring was unjustified.
Action on Smoking and Health (ASH) chief executive Deborah Arnott said: "The Directive is lawful and the UK is allowed to go further than the Directive in standardising tobacco packs with respect to matters not harmonised by the Directive."
Image: Standardised packaging expects to help lowering smoking rates in the UK. Photo: courtesy of Cancer Research UK.