I thought it was commonplace (maybe among common lawyers) that personal correspondence was copyright in the author — so the recipient of a letter can't publish it without permission. (slaw.ca)
The Mobility Protocol with Quebec expressly prevents common lawyers from practising anything other than their local law (say Ontario) as non-Quebec legal consultants, or federal law (say tax, patents, immigration or criminal law). (slaw.ca)
The Convention was the work in large part of British common lawyers. (newlawjournal.co.uk)