At least in the Netherlands this would still constitute unauthorised copying of licensed material, and therefore be illegal.
Honestly, the question in this case then becomes βhow will anyone be able to enforce it?β
ISPs can be compelled to share name/address information of anyone involved in publishing licensed material through the courts. Then theyβll summon you to stop or pay a fairly hefty fine.
Youβd have to first establish that the person under the IP is actually sharing copyrighted material. This is easy to track on something like BitTorrent, but virtually impossible through a regular website. Youβd have to have someone pretending to be your friend, getting access to your song and then filing a complaint.