The 57-year-old woman was stopped by police near Laholm in southern Sweden in March of least year on suspicion of being under the influence of drugs.
Subsequent test revealed she had both methamphetamine and amphetamines in her system, resulting in charges for minor drugs offences, the local Hallandsposten (HP) newspaper reported.
During her trial, which was held on Wednesday in the Halland District Court, the woman admitted to ingesting the drugs, but explained that she had taken them in Denmark, where the drugs she used are not illegal.
As prosecutors were unable to prove the woman was lying about when she took the drugs, the court ruled that the charges be dropped.
"The crime happens the second you take the drug. The fact that she still had it in her blood when arriving to Sweden doesn't mean she has committed a crime in Sweden," lead judge Jenny Hayden told the newspaper.
However, the court's ruling didn't sit well with police officer Ulf Bejrum.
"This means that practically every person in the south of Sweden could say, 'I've just come back from Denmark,' and get away with taking drugs," he told HP.
Bejrum added that he hopes that laws will be amended as a result of the verdict in order to prevent other suspected drug offenders of using the "Denmark defence".