Summary

Yosef Karo Shulchan Aruch — Choshen Mishpat 25

We do not, however, rely on the words of an inferior against someone greater than him in wisdom or number, even if it was a pressing matter, unless there was a great loss at sake. Similarly, wherever an individual opposes the majority, we follow the majority. Even if the majority does not have the same rationale and they each have their own reasoning, since they agree on the law, they are considered the majority and we must follow them. If the city had a custom to be lenient because they received such a ruling from a scholar, they may follow his view.
Source: Wikisource

Yosef Karo Shulchan Aruch — Choshen Mishpat 25

See the end of Siman 3 for how permission from the king can help. A person should not say I will rule however I see fit on a matter that is a dispute. If he does so, this is a false ruling, unless he is a great scholar and knows how decide based on proofs, in which case he may day so. If he is not of that stature, he cannot take away money when in doubt because anytime there is a doubt in the law, we do not take away money from its current possessor.
Source: Wikisource

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