Every pilotage authority may, by byelaw made under this Part of this Act, exempt the masters of any ships or of any classes of ships from being compelled to employ qualified pilots, and annex any terms and conditions to those exemptions, and revise or extend any such exemptions or any exemptions existing by virtue of any Act of Parliament, law, charter, or usage, upon such terms and conditions and in such manner as may appear desirable to the authority.