weird, the rules still say "first or business" and still explicitly include canada and mexico.

https://www.delta.com/us/en/delta-sky-club/access

oh, they've added a section for DL metal specifically that only specifies Delta One.

But the SkyTeam flight section is the same. And DL flights are SkyTeam flights.

Did the agents scan your boarding pass at any point? Do you have a copy of them? I believe it should say Sky Club on it if you are allowed access. As others have indicated, FC flights to Canada should qualify as an international Skyteam premium cabin flight. Although they've split up the sections, the language on the website really hasn't changed. Here's what it used to say (snapshot from March 2017).

Delta One or SkyTeam Premium Cabin Passenger

Customers traveling in Delta One on an international Delta flight or a domestic Delta flight connecting to/from a same-day international Delta flight* in Delta One or travel in international First/Business Class on a SkyTeam-operated flight. (In order to qualify for Club access, the customer must be confirmed in the premium (first or business class) cabin for the international segment of their itinerary.)

*International Travel includes: Customers traveling to/from Europe, Asia, South America, Central America, Africa, Canada and Mexico (excludes travel to/from the Caribbean, Guam, Palau and Saipan).

I don't think appealing to the skyteam rules is going to work here. STE+ will still get access regardless of cabin. This seems to only apply to non-STE+ passengers on F tickets.

The best all of the quibbling will yield is a clarification that a ST F/J ticket must be operated by a DL partner.

The language seems fairly clear in OP's case. Yes, Canada is included. But, as he was not in D1, he is not eligible for SC access. The fact that there are no D1 flights to Canada may make the language superfluous, but won't change the result.

I will be testing this in a few weeks. I'm on a flight to Mexico in paid first class. The old language and new language are essentially the same. So far as I'm concerned, I'm traveling on a Skyteam flight. The language even links to a "list of Skyteam member airlines" and (of course) Delta is on that list. If they meant to exclude Delta "skyteam" flights they should have said so.

Is it a big deal? Nope. In the scheme of things, it's definitely a first world problem. However, having lounge access on the outbound flight is one of the reasons I choose to pay for first class. It's gonna suck if they now decide that I don't because it's not Delta One, although it is a Skyteam first class international flight.

BP doesn't say Skyclub unless an actual member.

Couple of different access methods are being discussed. Delta One regardless of route (including domestic D1 routes) gets access. Premium passengers meaning business/first passengers on international routes excluding Caribbean also get access. The problem is some DL agents are trained to only think of D1 as being international business. If the poster gave his BP for the flight to Canada I'm betting it scanned fine. However the agent decided the system was wrong.

BTW co-worker flew F to Canada first week of December and had no issue getting in. There has been issues for years with agents saying Canadian flights don't get access. Nothing new sadly.

That's not what the rules say anymore.

Actually, the poster's agent most likely followed what the system said (no access) and the agent in your cow-orker's case decided the system was wrong and (incorrectly) let him/her in.

It says so right here. This is same as it has always said.

I have had non-status friends fly FC to Canada in the past and have had no problems getting SC access. In fact, I've used my miles a couple times to book a friend in FC for his occasional trips ATL<>YUL and when in FC on that route, he makes a point to stop in the SC since he usually doesn't have access.

If DL is now interpreting their website language as DL-operated, "First Class" travel from US to Canada being ineligible for access, this represents a very real change in the policies and the loss of a benefit of the premium cabin travel "experience" on those flights.

The least they could do is be a little more clear in what the new access policies are.

read that ENTIRE section. it's not the same. The definition of "international" is the same but that's only relevant on skyteam flights, there is different wording for delta metal.