An EU citizen’s right to freedom of movement is provided for in chapter 10 in the Foreign Nationals Act.
An EU citizen can be considered exercising his or her right to freedom of movement, if he or she moves to or resides in another member state than the state he or she is a citizen of. This also applies to an EU citizen’s family member who accompanies him or her or follows him or her later.
The aforementioned instructions for EU citizens also apply to citizens of European Economic Area Member States and citizens of Switzerland and their family members.
EU, EEA, EFTA and Schengen countries - Finnish Customs (tulli.fi)