Houston Dynamo traveling supporters have reportedly had their Supporters Group Exemptions indefinitely revoked by MLS because of actions during the most recent MLS Cup (via Dynamo Theory). According to a image captured email, Dynamo supporters have been banned from bringing such items as banners, drums and flags on the road after several members of their group were seen throwing items onto the field.
The punishment, if being reported accurately, would be particularly harsh and has to be seen as a step backward for supporters groups all around the league. Supporters groups have made significant inroads in recent years, especially in terms of the atmosphere they help generate, and banners, flags and drums are a significant part of that.
That said, part of the reason MLS has allowed for supporters group exemptions in the first place is because there is an expectation that groups will police themselves. If Dynamo supporters were throwing smoke bombs or other dangerous itmes onto the field, that's a potentially significant safety hazard and some kind of punishment had to be expected, even if this does seem to be over the top.