The Metropolitan Police has said it is taking no further action against an MP who travelled by train from London to Glasgow after testing positive for coronavirus.
The force said Margaret Ferrier had not breached laws in England which require people to self-isolate because she was tested before they came into effect.
The case is now being examined by Police Scotland.
Ms Ferrier is sitting as an independent MP after being suspended by the SNP.
She has refused to quit as an MP, and said coronavirus made her act "out of character".
The MP for Rutherglen and Hamilton West was tested for coronavirus on Saturday 26 September because she had a "tickly throat".
While awaiting her results, she is believed to have gone to church on the Sunday before travelling to London by train on the Monday.
She spoke in the Commons later that day, before finding out a short time later that she had tested positive for Covid-19.
Ms Ferrier then decided to get a train back to Glasgow the following day, fearing she would have to self-isolate in a hotel room for two weeks or her condition could worsen.
In a statement, the Met said it had considered possible offences under the Health Protection Regulations 2020, which makes it an offence for people in England to come into contact with others when they should be self-isolating.
The force added: "On detailed examination of this new legislation, and following legal advice, it was concluded that this regulation is applicable only after the 28 September.
"In this case the test occurred prior to the 29 September and therefore the regulation does not apply.
"As such, there will be no further action in relation to this investigation from the Metropolitan Police."
It added: "We are in liaison with Police Scotland and have referred the matter to them for consideration."
In Scotland, self-isolation is guidance rather than a legal requirement.
However, Police Scotland said it would now assess the circumstances of the case and consult with the Crown Office and Procurator Fiscal Service "before taking a decision on next steps."
Ms Ferrier's actions have been widely condemned, with cross-party calls for her to resign as an MP.
First Minister Nicola Sturgeon, the SNP leader, said the MP's actions had been "utterly indefensible" and called for her to step down.
And the speaker of the House of Commons, Sir Lindsay Hoyle, said he was "very, very angry" at Ms Ferrier's "reckless" behaviour.
Although Ms Ferrier has been suspended by the SNP, the party is unable to force her to quit as an MP.
However, the Scottish Conservatives have called on the SNP to expel Ms Ferrier from the party.
Ms Ferrier defended her actions in an interview with the Sun on Sunday at the weekend, saying she had panicked at the prospect of having to self-isolate in a London hotel after testing positive.
The MP added that she did not deny that she had made "a serious error of judgment", but said she wanted to continue representing her constituents and dismissed the incident as a "blip".