I have just two points. One, it's easier in the U.S. to define lobbying because lobbying is not tax deductible. Their national customs and revenue has defined what is lobbying and what is lobbying activity, and therefore expenses are not tax deductible.
The other thing is that it's not a question of ethical or unethical; it's a question of people having the choice of whether they want to register the activity or not. It still remains that people can make that choice. They can skirt the law. They can decide, “I'm going to go this way so that I don't have to register or be visible in the process”.