It means you could be legal to drive in England, but be over the limit once you cross the border. Scotland's new tougher drink-drive limit's already been responsible for four arrests within the first six hours of the new being operational.
The lower limit's been brought in line with much of Europe, and is now almost half that of the rest of the UK. Almost eight in 10 Scottish motorists support the reduction, according to a survey by the RAC.
The Free Church of Scotland also believes the measure is supported by the majority of its members, speaking on Premier's 'News Hour' retired Edinburgh minister Revd Alex McDonald said: "I think it's the rest of the UK that are out of step with the rest of Europe on this question."
There are proposals in Northern Ireland to follow suit, but there is no such thirst for change south of the Scottish border.
Experts have said the new 50mg limit, which came into force at midnight, means that an average man would be limited to just under a pint of beer or a large glass of wine, and women to half a pint of beer or a small glass of wine.
Revd McDonald also insisted that people taking wine at Holy Communion should have no concerns about getting in the car and driving after church, he said: That's just a tiny amount of alcohol, of wine. So, no that certainly wouldn't put any body over."
Road safety organisation Brake welcomed the reduction, but called for a limit of just 20mg to be introduced.
Deputy chief executive Julie Townsend said: "We are calling on the UK Government to take action on drink-driving.
"We have the highest drink-drive limit in Europe, sending out the dreadful message that a drink or two before driving is acceptable. The evidence shows that a tough approach helps prevent casualties."
Revd Alex McDonald, Free Church of Scotland:
