The competent authority is the minister, government department or other authority that issues and enforces regulations, orders or other instructions and the force of law for a certain provision. In this case, the MLC.
Not every country in the world has ratified the MLC. Those who have ratified the MLC need to have identified a competent authority to be response for the MLC and its implementation.
Seafarers have the right to report MLC violations to the competent authority.