Reasonable belief is a well understood concept. It doesn't need a definition in the terms of service. A judge reviewing a complaint by a party against Samsung will understand what "reasonable belief" means.
> But you still have no digital rights.
I think you're confused. It seems like you want Samsung to not have digital rights. You have digital rights, but not to use someone else's system in a manner which they don't want. If they operate a system, they have a right to specify how users can and can't utilize the system. You have the same rights.