Moving cryptogams across state borders

Hi all,

A number of prominent researchers in the field maintain that importing and exporting live non-invasive mosses/lichens/liverworts is normally very legal as long as the package does not contain soil. This is despite the fact that numerous endobiont microanimals and fungi often reside within them and cannot be removed easily (see

How would one go about preventing said endobionts from being invasive after exportation without expensive scientific equipment or total sterility?