It was recently announced that Switzerland had denied America's request to extradite the director in order to answer charges stemming from the 1970s stating that he had sex with an underage girl. He was subsequently released from house arrest.
However, US State Department spokesman Philip Crowley insisted that he would appeal the case, reports WENN.
"[Sex with] a 13-year-old girl by an adult who should know better and does know better is a crime," he said.
"We will continue to seek justice in this case and we will evaluate our options... This is not a matter of technicality."
Polanski also released a statement, thanking his supporters for their encouragement throughout the ordeal.
"I simply want, from the bottom of my heart, to thank all those who supported me and tell them today of my great satisfaction. Massive thanks to everyone."
One of Polanski's alleged victims, Samantha Geimer, recently said that she agreed with the decision not to extradite him to the US.