Yes...and no. All non-navigable intra-state inland lakes--iow, they're wholly contained within the boundaries of a single state, and they only way to get a boat on or off is launch ramp or a hoist--are "no discharge" waters..which means holding tanks only, no treatment devices of any kind.
However, treatment IS legal on almost all the navigable interstate waterways (rivers), including dammed "lakes" on them.
I see you're in KY...if you're asking about Kentucky Lake or Lake Cumerland, they ARE part of a navigable interstate waterway system, making treatment devices legal on them. But I'd go with the PuraSan
Raritan Purasan EX , which is designed for use in fresh water, instead of the ElectroScan which needs salt.