The GOF guidelines are not legally binding but common practice for actors on the Belgian SMS market (telecom operators, content providers and service providers).
Nevertheless, a content provider who doesn’t follow the rules can be fined by the telecom operator. This could for example happen if an end user reports to the operator that they receive a lot of spam SMS from the content provider.
A content provider who doesn’t follow the guidelines may also be cut off from traffic by the service provider. It can also lead to that the service provider (such as CM) refuses to distribute their SMS messages to end users.
It is in the interest of all parties involved that the guidelines are being followed. Not only because it reduces friction and makes collaboration easier. It also builds customer trust and improves the general approach to wholesale SMS among end users.