[@Willy Vereb]

The Interstellar economy is highly developed. Very few, if any, planets are actually capable of autarky anymore. Blockading your own system would effectively immediately remove your ability to fight the war, and once the enemy eventually clear the mines you're doomed. 

You can certainly try to seal yourself off, but given any gate can connect to any gate you're just hurting yourself. Moreover, I imagine (given the ITC, a power bloc) that by now a number of treaties regarding gate commerce have been passed, or forced, by or onto the governments of the Cluster.

So sure, you can cut yourself off. Your people will probably starve and your economy is almost certain to collapse, but don't worry! Once you eventually open your gate again you're going to be sanctioned and persecuted by just about every major trading nation.

That's my take. Sigma and Hyper can chime in if their opinions differ.