Based on the last section, it looks like it's retroactive.
There is more interesting bits...
This is related to cancellation and amendment of immigration documents.
87.304 (1) A person must answer truthfully all questions put to them by an officer that relate to the application of an order made under subsection 87.302(1) and must produce a visa and all relevant evidence and documents that the officer reasonably requires for the purpose of the application of such an order.
Obligation — appear for examination
(2) A person must, on request of an officer, appear for an examination — including a medical examination — that relates to the application of an order made under subsection 87.302(1).
This is troublesome... It means a person who is PR in Canada and falls sick or develops medical issue then IRCC can force him/her to appear for a medical exam persuant to a Governor in Council order and then cancel his/her PR Card. It is basically applying medical inadmissibility criteria in perpetuity on a PR unless he or she become a citizen... They can this way apply this medical exam anytime they want to. During PR card renewal, during citizenship application, during ... basically anytime.
There is a reason why this exam has been explicitly added to these obligations upon a PR...
Importantly, as these a Governor in Council order, they do not require ANY kind of legislation. This is a real devious move.
Since they recommend such kind of cancellation for persons in Canada be endorsed by minister of public safety, this can be a tool for "public interest" to show that how PRs are costing us X amount of money in health care so let us cut that money by kicking them out because we had their tax dollars anyways.
More interestingly, this is added as a "transitionary measure".... wonder why.