Internal Arrangements for Labor Law Compliance
That is an internal arrangement depending on the organization's structure and the line of command. There are no clear or strict rules.
Mostly, the HR department and the Compliance Officer (if any) will ensure that labor laws are being followed. In case of any inquiry, the concerned HR team will handle it. If the matter is serious or has critical implications, the Legal and HR teams will work together.
If the matter goes to court, then, of course, it will mainly be handled by Legal with input and assistance from HR where required. However, as I said, it depends on how your organization is structured.