Revise local board of health sanitation powers and rules

This bill amends Montana's public health laws to restrict local boards of health from adopting sanitation rules that exceed state standards and to exempt existing subsurface wastewater treatment systems from new local rule changes. It directly affects local health departments and private property owners with on-site wastewater systems by limiting their regulatory authority over sanitation enforcement. The key provision removes the ability of local boards to create stricter sanitation requirements than the state mandates while preserving their power to enforce state-level standards and address public health nuisances. Additionally, the bill ensures that wastewater systems already installed and functioning remain unaffected by future amendments to local health rules.