I don't understand this take but I'd like too.
Is there something about physically going to a place that is different than being in contact with their international counterparts?
Would your view change if you could be certain that everyone involved in these meetings is crystal clear that the opposition leader does not represent the sitting government and has no direct involvement in official diplomacy?
Are you familiar with the concept of shadow ministers? (I am not trying to insult you here).
God forbid someone think I'm being positive about the canadian government but I think it's contrary to the idea behind a parliamentary system to have the ruling party dictate who the opposition can meet with or where they can travel (with higher scrutiny than is applied to the general population).
I think getting advice from Global Affairs is probably a good idea. The staff (not the minister) are not tied to a party and have a lot of knowledge and experience to draw from. There is no way any politician can be up to speed on everything the way someone who has been solely focused on a particular area can.
There are mechanisms to deal with situations that are considered harmful. For example, on the provincial level Goldie Ghamari was expelled from her party in Ontario because she met with Tommy Robinson (virtually). Party members are beholden to their leader if they want to stay in the party, but individual MPs including the Leader of the Official Opposition are not beholden to the PM or their party. People can object to their trips but that's different than requiring them to get permission.
There are also specific rules about what they can and cannot do, and this is not tied to who is in charge: https://lois.justice.gc.ca/eng/acts/F-29.2/FullText.html
For example, this article talks about MPs going on sponsored trips, what is allowed and why MPs say they go on these trips: https://www.cbc.ca/news/politics/members-parliament-sponsored-travel-9.7140842
One of the reasons I feel very strongly about the freedom to travel and learn from others is my personal experience of working at an org where no one traveled or sought to see how others are doing things. As a result, they were easily swayed by lobbying and sales pitches because they only knew what the sales people told them. They were also extremely reactive to legislative changes that they could have been forseen and they could have provided consultation feedback for if they paid attention to anything outside of their fence line. I might have ignored implied pressure to not travel to events myself on occasion 🫣
Yes, it's annoying to hear about the grandstanding people sometimes do on these trips, but I'd rather suffer though that mild annoyance and hope some member of the delegation learned something useful they can bring back.