concerning; over; about; centering on
Used to introduce a topic of debate, conflict, or discussion. Often followed by verbs like 議論する, 争う, 話し合う. The phrase is a fixed expression derived from 巡る (to go around).
See also: 巡る
A heated debate took place in the Diet over the new law.
その事件を巡って、さまざまな噂が流れている。
Various rumors are circulating concerning that incident.
に関して is a formal, neutral way to say 'regarding', whereas を巡って adds a nuance of dispute or active discussion about the topic.
Derived from the verb 巡る (めぐる, 'to go around'), in its te-form 巡って, combined with the particle を. The phrase literally means 'going around ...' and developed the figurative sense of 'concerning' or 'over' a topic of debate.