Complex sentence: The Dockyard Act, passed three months earlier in April, allowed those suspected of burning His Majesty's vessels to be tried in England, but this was not the law that was used against the "Gaspee" raiders; they were charged with treason.
Split into simpler sentences: The Dockyard Act, passed three months earlier in April, allowed those suspected of burning His Majesty's vessels to be tried in England. But this was not the law that would be used against the "Gaspee" raiders; they would be charged with treason.