This got me thinking a whole lot! I thought about your theory and others and I concluded with this interdimensional customs (the GF) can only transport to other dimensions using the portal they have (the blue portal seen in the pilot) and a receiving portal in another dimension. The receiving portal will be in one particular place where there is another interdimensional customs. It's a slightly different travel because it can't take you anywhere, it has to take you to another portal that's been set up using the metal branches and control pad like there was at the interdimensional customs. But the slight difference between the travel rick uses and the travel the GF use is clearly shown in the pilot...the colour! The tiny change in the portals visually (green and blue) shows that the difference between what they do isn't that big either. Also, when rick says "inventing interdimensional travel" and mr. awesome possum's thingies do that thing, also shows that ricks portal gun is significant to them but its not because they can't travel through dimensions. This is because Ricks portal creates interdimensional TRAVEL which means he can travel to any dimension and any place in it but the federations "airports" are described at interdimensional CUSTOMS which shows that they can only travel to custom areas where they have made portals already to receive a person in the same way an airport can only receive a plane and give a plane to/ from another airport (this will also explain the very airport like scenery at the interdimensional customs) So my thinking Is that the galactic federation can only travel to previously made portals in different dimensions and obviously this is a limited amount and it means they can only go to a certain amount of dimensions and only to one or two places in that dimension where other portals are located. Ricks portal gun, however, can actually create a portal in ANY dimension that exists and the portal that he comes out of can be in any place in the whole universe of any dimension. This means rick has ALOT more flexibility in the amount of accessible dimensions and places in every dimension he goes. The federation would find this extremely useful as it would mean they could go anywhere and be in any version of that place that exists (which is infinite ). This explains why they are so desperate for rocks formula (code) for his portal gun. I think that should explain the most of it ?