All Those Qualified May Interpret the Law, but They May Not Be Lawgivers
Everyone capable who is qualified to practise ijtihad, may interpret matters for himself which are not incontestable; and they are binding on himself but not on others.
He cannot make laws and call on the Umma to conform to them. His ideas are from the Shari‘a, but they are not the Shari‘a. He may be a mujtahid but he cannot be the Lawmaker.
The Shari‘a is ratified through the consensus of the majority of scholars. The first condition for calling on others to accept an idea is the surmised acceptance of the majority.
Such a call is otherwise innovation; it gets stuck in the gullet, never again to emerge!