"Have they abdicated their responsibility ?" Nope.  

They are arresting and detaining them under the Immigration and Refugee Protection Act and turning them over to Canada Immigration for processing.

There is a very good legal reason why refugee claimants (not asylum seekers which are a completely different class of persons) are not being charged in respect of their entry to Canada.

Under Article 31 of the 1951 Convention on Refugees Canada has undertaken to not prosecute refugee claimants for illegal entry into Canada including any issues of false documents or fraud relating to that entry.

Canada has enacted that exemption into our domestic law as required by the Convention in various iterations of our immigration legislation over the years. Currently that exemption is contained at s. 133 of the Immigration and Refugee Protection Act.

So no charges because the law exempts refugees recognizing that refugees who are fleeing persecution are different from other migrants.