§ 12. Preferential claim; not assignable or subject to attachment; attorney's fees. Any person entitled to weekly payments under the plan against any employer shall have the same preferential claim therefor against the assets of the employer as now allowed by law for a claim by such person against such employer for unpaid wages or personal services. Weekly payments due under the plan shall not be assignable or subject to attachment, levy or execution. No claim of an attorney for any contingent interest in any recovery under the plan for services in securing such recovery shall be an enforceable lien thereon, unless the amount of the same be approved in writing by a justice of the supreme court, or in case the same is tried in any court, before the justice presiding at such trial.