I have just handled a number of files that involve criminal inadmissibility issues and gone through the process of obtaining a TRP for my clients that were deemed to be criminally inadmissible to Canada.
In this case, we are taking about foreign nationals seeking to enter Canada (eg. as a visitor, or as a permanent resident). One essential step is to obtain the client's criminal record. This may involve an offence in Canada or outside of Canada. Also - obtain a copy of the offence, and get full details on each offence.
If the offence occurred outside Canada, an 'equivalency' must be done - essentially you have to determine whether the foreign offence has an analogue or equivalent provision in Canadian law. You are in luck if the individual has committed an 'offence' in the foreign jurisdiction which is not a criminal offence in Canada (Canadian standards apply).
An assessment can now be made whether the individual is in fact inadmissible to Canada - and this is done by taking a look at the nature of the offence and how it is treated in Canada. Once all the relevant factors are considered, the individual can be advised whether or not they will be held to be inadmissible to Canada for criminality.
Even if the individual is inadmissible, there may be options including pardons, deemed rehabilitation (not available for offences in Canada, unless the offences are summary conviction offencees only) or entry using a TRP.