The UK's highest court has rejected a long-running challenge against plans to use minimum pricing for alcohol to improve public health in Scotland. Here are some key questions about the proposal:

What is Minimum Unit Pricing?

Minimum unit pricing, or MUP, simply sets a floor price for a unit of alcohol, meaning it cannot legally be sold for less than that. The more alcohol that is in a drink, the more expensive it will be. The Scottish Government insists that MUP is not a tax, but is rather "a targeted way of making sure alcohol is sold at a sensible price".

Why does the price of alcohol matter?

Health campaigners argue that when the price of alcohol goes down, consumption of alcohol goes up. The more affordable drink becomes, the more people use it, and the more harm society experiences because of it. The organisations Scottish Health Action on Alcohol Problems (SHAAP) and Alcohol Focus Scotland are among those to have campaigned for an increase in the price of drink to cut consumption and harm.

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What exactly does the Scottish Government want to introduce?

The Alcohol (Minimum Pricing) (Scotland) Act 2012 was passed by MSPs at Holyrood in 2012. The Scottish Government's preference at the time was for alcohol to be sold at a minimum price of 50p per unit. It believes MUP will mostly affect the cheap white ciders and value spirits with high alcohol content that tend to be favoured by harmful drinkers. A 50p minimum price would mean a 70cl bottle of whisky could not be sold for less than £14. It would take the cost of a 70cl bottle of 37.5% vodka to no less than £13.13, four 440ml cans of 9% lager would increase to a minimum of £7.92 and a 75cl bottle of 12.5% wine could be sold for no less than £4.69.

What's wrong with bringing in other measures instead?

Ministers insist that Scotland's alcohol problem is so significant that "ground breaking" measures are needed. They say that, given the link between consumption and harm and evidence that affordability is one of the drivers of increased consumption, addressing price is an important element of any long-term strategy. Ministers believe there is strong international evidence that tackling price, as part of a package of measures, can help reduce alcohol consumption.

READ MORE: This is how much booze will cost in Scotland under new minimum pricing rules

Just how serious is Scotland's relationship with the bottle?

The Scottish Government argues that the nation's relationship with alcohol has become imbalanced. Almost a fifth more alcohol is sold per adult in Scotland than in England and Wales, and statistics show that more than 40% of prisoners were drunk at the time of their offence. Recent figures also reveal that alcohol-related deaths have increased by 10% over the last year whilst in other European countries outside the UK and Ireland they are falling. On average, alcohol misuse causes about 670 hospital admissions and 24 deaths a week and it costs Scotland £3.6 billion each year, or £900 for every adult, ministers say.

What impact could MUP have on harm reduction?

Ministers say it means less money will have to be spent dealing with the consequences of alcohol misuse. Alcohol Focus Scotland says that in the first year alone, minimum pricing could prevent 60 alcohol-related deaths, 1,600 hospital admissions and 3,500 crimes. The Institute of Alcohol Studies says analysis found that a 50p MUP would have minimal effect on moderate drinkers, while heavy drinkers would drink 134 fewer units a year on average.

The legislation was passed in 2012, so why doesn't Scotland have minimum pricing for alcohol yet?

Implementation of the law has been held up due to the long-running legal challenge from alcohol industry bodies, led by the Scotch Whisky Association (SWA). Their challenge has already been heard at various levels at Scotland's highest civil court, the Court of Session, and gone to the Court of Justice of the European Union. It was only after that, that the hearings moved to the UK Supreme Court.

READ MORE: Minimum alcohol pricing drive in Scotland - the timeline of events

What are the arguments against MUP?

The Scotch Whisky Association (SWA) believes it will not tackle alcohol misuse effectively and says there is no evidence that MUP is effective in reducing alcohol-related harm. It believes that the measure contravenes EU trading rules. It claims MUP will set a precedent for "equally ineffective and illegal measures" by other countries which could severely damage the Scotch Whisky industry's export markets and the Scottish economy. The body says it is a regressive policy that hits responsible drinkers, in particular those with the lowest incomes. They agree there is a problem with alcohol misuse but say alcohol-related harm in Scotland has declined in recent years. In addition, existing laws on under-age sales and sales to drunk people are not fully and effectively applied at the moment, it argues.

How soon could the Scottish Government implement the policy?

Ministers have always said they will move "as quickly as is practicable" to put the policy in place.