The controversial UK Internal Market Bill would mean a "higher bar" for measures which potentially discriminate against fair market access for goods from outwith Scotland, an advisor to Holyrood's Constitution committee has warned.
The groundbreaking policy was held up in the European courts for years after legal challenge by the Scottish Whisky Association before finally being introduced two years ago.
The UK Government rejects claims that the controversial legislation, which will breach international law in limited areas, will have any impact on Holyrood's ability to raise the minimum alcohol price.
Amendments have even been lodged to the Bill stating that price controls are not "relevant requirements" for the purposes of the legislation which seeks to create a single UK market when the Brexit transition expires at the end of the year, replacing the European single market which will no longer apply here.
But Professor Kenneth Armstrong from the University of Cambridge, advisor to Holyrood's Constitution committee on the Internal Market Bill, warns that issues may arise if minimum pricing is considered in the context of "indirect discrimination."
He explains in a paper to MSPs: “A Scottish rule that applies Minimum Unit Pricing to all alcohol whether domestic or imported could be indirectly discriminatory if it impacts more on imported alcohol than it does comparable Scottish-produced alcohol."
A three step test is set out in the legislation covering firstly whether an incoming good is put it at a disadvantage. Secondly it tests whether it causes an adverse market access effect, and thirdly whether it "cannot reasonably be considered to be a necessary means of achieving a legitimate aim."
Although the "protection of public health" is recognised in the Bill as legitimate aim, the advisor warns there could be questions raised around will be “reasonably” considered to be “necessary” to achieve this aim.
"It is a different test from the proportionality test applied by EU and UK courts in the Scotch Whisky Association case," he adds.
Professor Armstrong does say that even a revised minimum pricing scheme could be compatible with the new UK legislation, but it may be more awkward than previous EU laws.
"The approach in the Bill is potentially to set a higher bar for when a requirement is considered to be problematic indirect discrimination," he states.
"Given their novelty, the application and outcome of these new tests is unknown and likely to be tested in the courts."
The minimum price is currently set at 50p per unit, but there have been suggestions this could rise to 60p.
A UK Government spokesman said: “This advice agrees that the minimum alcohol pricing policy is compatible with our UKIM bill, and in some areas there are now higher protections."It has always been the case that this legislation would not impact Scotland's minimum alcohol pricing policy but we have acted to provide increased legal certainty around this point."Our amendment has further clarified the freedoms of all parts of the UK to regulate pricing and manner of sales policies as long as they are non-discriminatory."