Nationals of EEA member states and Switzerland can take advantage of unrestricted freedom of movement for workers and do not require a permit to work in the Netherlands.
To take up gainful employment in the Netherlands for up to 90 days, nationals of countries other than EEA member states or Switzerland (‘third-country nationals’) may need a work permit. Details are provided here.
Incidental employment such as taking part in a sports event may also be exempt from work permit requirements.
See furthermore the information on posting workers, below.