Dear Devdatt.
If you define DG Schema for your Logistics process , once you click on save or run the DG Checks in your Sales Document it will routes to your material basic data 2 view and check whether Dangerous goods profile is maintained or not(Ex : GPP ) , if it is maintained the it will go to Dangerous goods master record of that material (DGTMD Table) it will check the impressibility indicator with respective route (Ex:Road in below Screenshot). If indicator is there for that Route it will not allow the material through that route.
If iam not wrong in your case , if Product X is shipping from one country to one country in different routes Like Air ,Ocean &Road. If your Product is restricted to ship through Air , the Above indicator should maintain in DG Master against the Mode of transport. Then automatically in logistics process system will restrict you product to ship in that particular route . you will get the message pop up "Material cannot be transported with this mode-of-transport category" .....
If your issue is different from my above explanation can you please brief your issue with screenshots.
Balajee