The group Generation Identitaire said in a statement that its activists "took control" of two bridges Saturday and wants EU and national governments to reinstate borders.
The regional police department said 14 were detained and a truck seized to show the government's "determination not to let extremist movements manipulate the migrant crisis," the Associated Press reported.
Calais, long a magnet for migrants trying to sneak across the English Channel to Britain, became a flashpoint in Europe's unprecedented wave of migrant arrivals.
Thousands of people escaping war in the Mideast and Africa gathered in a filthy Calais camp that authorities are gradually dismantling.