Effective May 24, 2017, Dig Through Time, Strip Mine, and Treasure Cruise are banned in 1v1 Commander.
Wizards released the following statement on their official MTGO Tumblr:
Strip Mine
In conjunction with Life from the Loam and Crucible of Worlds, Strip Mine recursion locks have proven to be an extremely powerful and resilient lock taking minimal investment from the decks playing them.
Dig Through Time/Treasure Cruise
Initial results have shown that blue midrange decks, either mono-blue or Sultai-colored, are rising to the top at a steady rate. Given the variety of Commanders being played in decks with similar strategies, this appears to be a color and strategic imbalance in the format more so than individual problem Commanders. While removing these cards is far from a crippling blow to these decks, it’s a clear first step in lowering their power level.
These bans, though unsurprising, are a problem of Wizards’ own creation. The announcement of 1v1 Commander leagues on Magic Online necessitated the creation of an officially-maintained banlist and, as LSV showed this week, this newly-supported format was awash in blue mirrors. In response, Wizards banned two of the most powerful blue cards in recent history, Dig Through Time and Treasure Cruise.
Reaction to the bannings has been mixed, in part because the 1v1 leagues and multiplayer Commander matches are both governed by the same banlist, resulting in cards that are problematic in 1v1 being banned in multiplayer as well. Wizards stated today that the banlists will become separate on July 5, 2017.