This article considers which legal regimes apply in cases where a Danish citizen and/or resident returns from Syria or Iraq after having taken part in the armed conflict on behalf of the group known as Islamic State, and continues his/her affiliation with the armed group. The article argues that international humanitarian law currently applies to the Danish territory and that a Danish foreign fighter may continue to be considered as taking a direct part in hostilities after having returned from Iraq or Syria. The article then considers the application of Danish criminal law to returned foreign fighters and argues that Danish counterterrorism laws do not apply to members of the armed forces of an armed group that is party to an armed conflict with Denmark.