The Internal Market Act was passed by the then Conservative UK government in 2020. It set out new rules on the trading relationships between the four nations of the UK following Brexit.
The Scottish government branded it a Westminster "power grab", while the UK government described it as "the biggest transfer of powers in the history of devolution".
The argument stemmed from whether Holyrood or Westminster should take control of powers being returned to the UK from the EU – such as rules over food and air quality and animal welfare.
The Scottish government argued any powers not specifically reserved to the UK government should automatically come to Holyrood.
Conservative ministers argued they had to take control of certain powers to ensure the "internal market" set a level playing field for companies across the UK – allowing Welsh farmers to sell their lamb in Belfast, and Scottish whisky distilleries to buy barley from English farmers.
They said without such a system there would be "serious problems" for trade across the UK.
Perhaps the most notable impact of the Internal Market Act came in the collapse of the Scottish government's bottle return recycling scheme.
The plans required an exemption from the act to proceed. But UK ministers refused to provide one without glass being dropped from the scheme.
Former Green minister Lorna Slater said she had no choice but to delay the plans, accusing Conservative ministers at Westminster of sabotage.