(Note: orders-in-council are ‘the government’. In short form, in this context they are basically the implementing regulations under the laws referenced).
There may be further detailed implementing instructions and the like published by the various departments clarifying certain aspects, like what documentation might be required.
Warning: as far as I am aware, none of the below removes the need for a visa.
-Immediate family of citizens and permanent residents will be allowed into Canada. (Note: this goes further than what the PM announced)
-Immediate family: the definition of immediate family is essentially the same as for immigration under “family sponsorship”: spouse, common-law partner, dependent children, and dependent children of the dependent child (and their dependent children).
Note: while this document does not specifically address whether COPR/visa holders will be able to enter Canada, for family class principal applicants (and their family members) – all of whom are sponsored by a spouse or common-law partner, these provisions should suffice to allow them to enter.
One small warning: as mentioned above, the airlines must let you board your flight. But this order-in-council is plainly and simply written mostly, and seems to use the definitions most are used to, so the airlines should be able to get up to speed fairly quickly. (Note, you can certainly print and bring a copy of the order-in-council with you to airport. Your mileage may vary, no guarantees, etc.
I do not know how this may apply to other categories of immigration, etc.
This is only my interpretation of the order-in-council – if any mistakes are found, please post in this thread. I also expect most will want to hear experiences of others actually travelling and whether it all goes smoothly.