From what I understand, it’s mostly a question of meeting each country’s minimum energy and velocity requirements rather than an outright ban on lighter calibers like the 6.5x54 MS. In parts of the UK, especially for deer stalking, older 6.5x54 loads have struggled to meet the legal thresholds, which is why people sometimes think they were “banned.” Modern loads or handloads can sometimes bring them back into compliance depending on the region and game species. The cartridge itself still has a long reputation for excellent field performance despite the regulations.
