It is perfectly fair for everyone to try hard to control Japanese knotweed. But threatening criminal prosecution and heavy bureaucratic procedures (waste licensing, waste transfer notes etc) just for moving it seems to me excessive.
The Environment Agency already states in its own Code of Conduct on knotweed that:
Where you rely on the methods of on site knotweed management in paragraphs 4.1, 5.4 and 5.5 this would normally require you to have a waste management licence or a pollution prevention and control permit.
However if you carry out these activities in full accordance with this code of practice, and the work meets the waste relevant objectives described above, then in accordance with our Enforcement and Prosecution Policy we would not normally prosecute for failure to have a waste management licence or permit.