The Commissioner of Lobbying clearly has the authority to investigate if someone is engaging in lobbying activities who is not registered when they should be registered. The law does not create penalties for public office holders who meet with people who should be registered but haven't. Again, the law is designed to put the burden on those who are engaging in lobbying activity to register, and there is a robust investigatory set of powers around the commissioner to investigate situations where that does not occur.
Evidence of meeting #37 for Access to Information, Privacy and Ethics in the 40th Parliament, 2nd Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was ethical.
A recording is available from Parliament.