"Shield blocking" or "shield glitching" has been in Siege since the game's inception, but had been banned in competitive play after its used caused controversy the last time we saw it years ago.
However, last week, ESL reconvened and ended up reversing the previous decision to ban the "tactic" from their tournaments and leagues. It's reintroduction only saw scarce use though (partly due to the fact it was only around for a short period of time), and most of this was in North America, though most of the players expressed disdain for it just like in the other regions.
Many people from viewers to current and former pros to casters spoke out against the decision to allow shield glitching, although its important to note that the disapproval was almost exclusively directed at ESL and their decision, not the players using it.
With the collective feelings of the community at large made clear, it was announced today by head ESL admin BK-201 that ESL would no longer tolerate shield blocking after its short, but not short enough, return.
In light of the return of shield blocking to the pro scene, many normal players saw an increased use of the shield blocking tactic in their own games. This lead to pressure being applied to Ubisoft to find a permanent solution to the in-game issue, after which community developer Its_Epi confirmed they would be working on a fix.