Travel restrictions will be put into place from Friday, with movement to and from level three and four areas against the law.
On Tuesday, the First Minister announced 11 council areas would be placed into a level four lockdown, the toughest restrictions possible in Scotland.
The areas – with a combined population of more than two million people – put into the top tier of the five-level coronavirus alert system are: City of Glasgow, Renfrewshire, East Renfrewshire, East Dunbartonshire, West Dunbartonshire, North Lanarkshire, South Lanarkshire, East Ayrshire, South Ayrshire, Stirling and West Lothian.
As part of the restrictions, which come into force from 6pm on Friday, it will be against the law to travel in and out of level three and four council areas.
Nicola Sturgeon said travelling outside of these areas could see other councils’ levels increase.
She said: “To put it bluntly – and we will require to monitor this – if we see evidence that people from East or South Ayrshire are visiting places in North Ayrshire, or that people from Glasgow are going to Inverclyde, we would have no choice but to put these areas in level four too.
“So it is essential that we all abide by travel restrictions.”
Sturgeon added: “To underline how important this is, I can confirm that the guidance that has been in place in recent weeks will become law from Friday.”
The Scottish Conservatives said there remained questions over how the travel ban would be enforced.
Holyrood leader Ruth Davidson said: “People across Scotland desperately need clarification on what this travel ban will mean for them.
“For this to be even remotely workable, everyone, especially those living near council boundaries, must know exactly where they can travel and the police need to know precisely how they are expected to enforce it.
“That clarity has to be provided before these restrictions commence on Friday.”