"to seal off" in Spanish

CONTEXT EXAMPLES
Context examples for "to seal off" in Spanish(!) These sentences come from external sources & may not be accurate. Therefore, we are not responsible for their content.
We need to promote fair and freer world trade rather than seal ourselves off by means of protectionism and fall back upon national markets.
Necesitamos un comercio mundial leal y libre, y no muros proteccionistas o retrocesos al mercado nacional.
That falls to the Belgian authorities, who were responsible for the decision to seal off the area surrounding the Community's institutions.
Ello compete a las autoridades belgas y fueron éstas las que decidieron aislar la zona que rodea las instituciones comunitarias.
I am resolutely opposed to the temptation to seal ourselves off in a Fortress Europe which would be bound, one day, by its very nature, to find itself under siege.
Estoy absolutamente en contra de la tentación de encerrarnos en una fortaleza "Europa" que estaría destinada, como toda fortaleza, a ser algún día asediada.