How modern authorities could stop Viking raiders at sea

How would modern governments deal with Viking raiders appearing aboard ships near their old European targets?

An offshore patrol vessel could use its 30 mm gun against the raiders' sails or masts and demand compliance, with a historian attempting communication in Norse.

In the imagined encounter, police, armed forces and enthusiastic historical reenactors would compete to confront the raiders. A Royal Navy offshore patrol vessel could demonstrate its reach by firing at their sails or masts with a 30 mm cannon. A historian would try to communicate a demand for compliance in Norse. The humor depends on the mismatch between Viking weapons and a modern patrol vessel's ranged firepower.