Admiralty charts from the UK, Australian charts & NZ charts are all copyright & cannot be legally copied. I have no knowledge concerning American charts.
However, as a navigator, this not the main issue. The problem is, and will always remain, whether the charts are up to date and whether you are able to correct your charts when required. I have seen foul ground alterations, new wrecks, new wave buoys, changing navigation light sequences, new offshore oil wells, new exclusionzones; the list goes on.
You need to be very careful.
SV The Fox