As quite a few of you might have experienced, the BG is blocking the transportation of government agents lists to planet Earth.
The reason for this is that we are playing our part in the RP: we (military) are protecting our interest, the names of fellow government employees: secret agents. It would be devestating if the list would get out.
When you approach a blockade, you will be warned not to proceed. You can get a chance to sell the cargo back at Los Angelos, hence loosing no money only a lot of time or drop it (after which it will be destroyed).
If you do not comply, force will be used to stop you.
Transporting other equipment like Sol Artifacts, Chemicals, VIPS and so on is not prohibited.
A good alternative to the LA - earth trading route is the "Prisoners run". Transporting chemicals from planet Manhattan to planet New Berlin, from there prisoners to planet Stuttgart and then luxery food back to Manhattan. It might not be that profitable as the Manhattan - LA - Earth - Manhattan route, but you will not find a police or military ship in your way.