[JesseK]

There is no rule which states that the open ports of a cylinder must be attached to the solenoid, which means that there is no reason venting directly to the atmosphere is illegal.

If it were made illegal via a new rule, I'd be pretty upset. We are working on a design that uses pneumatics and hasn't been seen in FIRST (or at least in the many designs I've seen or studied from 2008, 2010, or 2014). It's pretty simple, but relies on the pressure venting directly to the atmosphere. We could possibly overcome a ruling, but only by moving to more expensive solenoid valves.