Warplay did allow them at one point- Tor personally authorized me (and I believe at least one other person). They may have been doing it under the radar or, maybe they had to change insurance as their crowds have gotten larger.
The ASTM is responsible for the standards that most paintball companies adhere to (goggle impact protection, maximum size/weight of paintballs, etc). Tiberius Arms claims that the First Strike Rounds "comply with ASTM Safety Requirements" I suspect that the safety requirements define mass, diameter, force required to break. However, I understand that there is an ASTM definition of a paintball and it most likely says 'spherical' and may also say 'gelatin'.
I can't recall where I heard it (maybe it was a PB Extravaganza interview) but, I was given the impression that Tiberius Arms is currently working with the ASTM. This could mean they are lobbying for a change of the definition or, possibly having an approved specification. Time will tell.