If you want to limit the ways your service (or product) can be used, you can do so by explicitly arranging these limitations through a contract. Things that are already (otherwise) illegal do not have to be included in this arrangement (hopefully for obvious reasons).

Whatever is not explicitly forbidden by either law or contract, are not valid grounds for treating consumers differently.

Sadly, and mostly for historical and cultural reasons (and law enforcers not paying attention for a long time), it is often assumed that these rules do not apply to big service providers (and software producers alike). However, I have never found any legal basis for why such companies should be treated any different than any other one.