Personally, I would be concerned that the committee is taking action relative to youth positions of responsibility for anything other than conduct that might result in general revocation of membership. I can see the committee/chartered org saying “This youth is a hazard to others around him/her and can not safely participate in scouting activities,” although it would have to be a pretty significant hazard to motivate me to move in that direction (e.g. threat to life or limb, intentional hazing, etc). We have youth who have various degrees of medical/neurological/psychological impairment in our unit, and I only know of one circumstance where a scout was specifically asked to discontinue participation as a result of being an extreme hazard to others, after various attempts at accommodation of issues had been unsuccessful.
In general, it’s my experience that youth leadership positions are a program-side matter and are generally handled between the SPL and the SM, not the committee. The committee could reasonably establish bylaws requiring that all scouts with special needs (whatever those may be) be evaluated as to whether or not they require a parent to participate with the scout in order to ensure safety (e.g. newly-diagnosed diabetic who needs supervision to ensure appropriate frequency/levels of insulin dosing). I don’t see a blanket policy that would apply to the scouts in general as an issue. I would be concerned if the policy was crafted specifically to apply to this scout. That’s not intended as an accusation, mind, just a general statement of my view on policies.
I would also evaluate the decision based on what, if anything, was requested by the pack. If the pack no longer wishes the scout to serve as a Den Chief, then that’s entirely their prerogative, in my experience. I can see how the two committees might have coordinated on addressing that issue, particularly if they share a chartered organization. I would still have expected notice to come from the SM/SPL (depending on the SPL’s level of maturity and comfort with the issue) to the scout and his/her family, preferably with some indication of specifically what triggered the request and what corrective action would be necessary to be eligible to be reinstated, if possible.
Overall, it sounds like a situation that would be difficult to handle and evaluate, even with all of the specifics. Our unit agonized quite a bit over asking the scout in our case to disassociate from the unit, despite persistent problems. It’s a big step to tell a scout they can’t participate, even in as limited a way as revoking a position of responsibility.