All we know is that there are weaves that can interfere with the creation of gateways, and then counters to the counters can be attempted and so on. This therefore means that battles involving the One Power are fought on many levels.

Those were RJ's words.

So exactly how you interfere with the creation of gateways is open to speculation.

I think it would be pretty pointless if you had to actually SEE the gateway, since an enemy could then almost never be prevented from Travelling say into some basement of the White Tower or another hidden location within your perimeter defense.

To be of strategic value, a gateway interfering weave would have to be capable of warding an entire area from Travelling in some way.

That's my view. I'm certainly looking forward to seeing Demandred demonstrate it to us in the last book.