From the very beginning of the server, we had to block access to certain blocks, items or features. In the old days this was called 'List of Forbidden Blocks', which were usable by everyone, there was no implementation doing any proper blocking or monitoring. Enforcers were then supposed to check player inventories, search people, houses, chests, anything that could hold items.
Soon after we started using WorldGuard's methods to make the server block certain items and things from happening, and Enforcers pretty much got unemployed in that aspect. However, each time there was an incident, the resolution usually meant adding more stuff to the WorldGuard list. (for example adding workbenches to prevent people from crafting - which would hopefully reduce the amount of people trying to gather materials). We've evolved much from that aspect and our methods of protection as well, which is why WorldGuard's restriction will be heavily reduced.
Before the situation was
like this:
Nobody except staff may place/use/receive: fire, tnt, flint and steel, iceblocks, snow, buckets, bedrock, water and lava (both static and liquid), tracks, workbench, anvil, furnace, buttons, levers, pressure plates, redstone dust, repeaters, minecarts, sensors, portals, spawn eggs, ender eyes, xp bottles, fire charges, tripwire hooks, ender chests, beacons, comparators, block of redstone, ...
Most of these items were either added throughout history because of safety reasons or as measure after something happened. In others, it prevented excessive use of redstone and "possibly server intensive things" to stabilise the server (redstone constructs in particular)
Today there is a new list of restricted items which I think we can use. Summarised, this is what it looks like now:
Global Block are the collection of items unusable by anyone.
Right now it are mobspawners, spawneggs, experience potions and all variants of the minecarts.
Restricted Interaction and Usage is a collection of stuff that are considered as 'grey zone'. Right now: Bedrock, water and lava (liquid and non liquid), all types of buckets and the barrier block.
It's considered 'grey' because by default nobody can uses them except for Designers, Artists and Enforcers.
Redstone Restrictions is collection of all types of devices and items that could make a contraption work. The list is much shorter to what it once was, allowing more ranks to freely use the previously blocked items. Right now the server blocks all types of commandblocks, redstone dust, all the variants of carts, the redstone repeater and the comparator.
The list is still a work in progress, and if redstone would start to impact the server again (through running clocks, logic gates/circuits) these contraptions would be removed immediately