GARD was activated to be the Watchmen of the Federation, following the Coup by Alliance forces in Ross 128 in 3303, the subsequent 'liberation' of Ross 128 and the Warren Prison Mine.
Initially, GARD was nothing more than a research group, the brainchild of a retired Federal Navy black ops Colonel, tasked with observing insurgencies in Federation space and forming counter strategies.
Rumour has it that several plans to retake major Federation assets that had been lost due to inaction or incompetence, were put forward to Federal leaders by GARD, but the current climate of Federal indifference led to none of these plans or intel reports being acted upon.
Frustrated, GARD slowly repurposed itself for field operations and behind the scenes conducted recruitment and training involving some of the finest pilots and strategists in the Federation. In mid 3304 they emerged, stating "if nobody else is willing to protect Earth, GARD will", along with the slogan Ad Maius Bonum - For the Greater Good.
The Federation so far is turning a blatantly blind eye to GARD's activities, assumedly due to their connections and the simple reality that GARD is a convenient problem to have, having already shown the willingness and skill to cut through the red tape and accomplish major objectives that other more official units didn't dare touch.
Some witnesses have also reported seeing GARD ships present at trade hotspots, where they are warning undesirables not to interfere with legal trade and shipping or face the consequences.
Reports suggest they are always recruiting and use a dropbox for messaging at edgard.enjin.com. If you need to contact them, that's a good place to start.