Can we block conversion of records to other types?

[Guido1982]

I'm currently removing some 'ADD' buttons in related lists since we want to block some paths of creation. So for instance, we want to enforce users to create invoices from salesorders and very much prohibit them from creating invoices directly from accounts. Now I think removing the ADD button should be enough, but I was just wondering if we have some stronger way of enforcing (and prohibiting) certain paths of record creation/conversion.