I found out the hard way when a radio mailed to me from the States was seized by Belgian customs. It turned out the BIPT (Belgisch Instituut voor postdiensten en telecommunicatie) had been alerted of the parcel and seized it because I did not have a license. Now I can understand you need a license to own guns or an actual working radio transmitter, but this to me was really over the top. To their credit though, they soon did send me a letter acknowledging that this was indeed a historical piece of equipment and that an exception would be made in this case. I was allowed to request a license to own (not use!) this radio. To request a license, a list with details of all radios I already owned, along with a letter of motivation was to be sent to the BIPT. Now, over a month after the radio was seized, I have my license and the radio has finally arrived.
I know that practically all collectors and owners of WWII vehicles own a radio. Even if it no longer works, you need a license. I suggest you write a letter to the BIPT and be in order. An ownership license is free of charge. Let me know if you need any help.