As the result of a community referendum and then a unanimous council vote Canadian Highlander will no longer be played with the Sorensen Mulligan and will adopt the London Mulligan.
For a while now the council has wanted to try to align the format rules with those people are familiar with from other formats. This feeling combined with the resurgence of fast mana decks looking to push the limits of a second six mulligan led to the decision to adopt the London Mulligan over the Sorensen.