http://www.legislation.gov.uk/ukpga/2020/7/pdfs/ukpga_20200007_en.pdf?view=interweave

The UK lock-down was put into effect on 23rd March.

In the Telegraph, yesterday and repeated widely by opposition politicians and journalists, including BBC Reporting Scotland:

More than 2,000 coronavirus deaths could have been prevented if Scotland had locked down two weeks earlier [9th March], according to a study published as Nicola Sturgeon urged people to ignore Boris Johnson’s exit plan. A team of epidemiological scientists at Edinburgh University estimated that around four out of five deaths could have been stopped with earlier action, based on the behaviour of the Scottish population.

https://www.telegraph.co.uk/politics/2020/05/11/four-five-scottish-covid-19-deaths-prevented-lockdown-had-started/

The scientists and the media missed something important. From reader indyref2soon:

The Coronavirus Act, which allowed Scottish Ministers to take action was only passed into law on 25th March. Lockdown actions happened a few days in advance [23rd] of clearing the final, House of Lords, hurdle. Various folk on Twitter, including me, have pointed this out.This is the relevant section for Scotland:

 http://www.legislation.gov.uk/ukpga/2020/7/schedule/19/enacted?view=interweave

Another reader and contributor, stewartb, then hammered the nail home with this:

“The recently adopted Coronavirus Act 2020 DOES NOT CONFER NEW POWERS on UK and Welsh ministers to impose a lockdown on the people of England and Wales. It DOES CONFER such powers on Northern Ireland (specifically, the Northern Ireland Department of Health) in Schedule 18; and on Scottish ministers in Schedule 19.  NEITHER NORTHERN IRELAND NOR SCOTLAND HAD THEM PREVIOUSLY.” (my emphasis)

So according to this article, the SG did NOT possess the same powers as Westminster already possessed for England and Wales to allow it to establish a lockdown such as the one we have experienced. The SG and NI governments were dependent on new powers being granted to them by Westminster.

https://ukconstitutionallaw.org/2020/04/01/jeff-king-the-lockdown-is-lawful/