Authorities said the combination of letters was "offensive" and violated motor vehicle department rules.
The rapper, whose case attracted the attention of President Trump, was given a suspended sentence and will not face prison time.
Presidential hostage crisis envoy Robert O'Brien sent that message in a letter to the Swedish Prosecution Authority.
President Donald Trump commented on the rapper's release on Twitter.
Diplomat Robert O’Brien's appearance is another sign of the president's involvement in the rapper's case.
"We will make our voices heard," said the Swedish teenager who inspired the Fridays for Future youth movement for climate action.
"Political interference in the process is distinctly off limits," Carl Bildt wrote. "Clear?”
The U.S. rapper, whose detention has prompted a major international response, will remain in custody until his trial, prosecutors said Thursday.
"While you're at it, could you also let those kids in cages out?" the singer asked the president.
The rapper has been detained for his potential involvement in a Stockholm street fight.
The American rapper's ongoing detention has led to a public outcry from celebrities, hip-hop artists, politicians and fans.
Four lawmakers have called on the U.S. government to become involved in the case, citing "human rights violations" committed against the rapper.
The U.S. women are moving on to the knockout rounds of the 2019 World Cup after 270 minutes of nearly flawless soccer.
U.S. authorities are also seeking the WikiLeaks founder's extradition.
Swedish prosecutors have decided to reopen a rape case involving Wikileaks founder Julian Assange.
The WikiLeaks co-founder avoided extradition in the Ecuadorian embassy in London for 7 years.
The case against the WikiLeaks founder was dropped in 2017 because he couldn't be questioned in the Ecuadorian Embassy.
The Arctic city is moving 2 miles away to stop it falling into the mine that created it.
Everything at ReTuna is recycled, reused or sustainably produced.