A person to whom Regulation applies is subject to the legislation of a single Member State only.
There are some exceptions on this general principle applicable to certain persons and circumstances.
The purpose of this rule is to avoid the complications which might ensue from the simultaneous application
of a number of national social security systems and to ensure that the person does not fall between
the systems and end up without any social security coverage. The main rule is that the person is covered
by the social security legislation of the Member State of gainful activity.