The DEA is a relatively new organization, formed in response to the spread of Elvish cultivation of mage weed.
For thousands of years, mage weed was only a mild intoxicant. Somewhere around 50 years ago, Erevan Ilsere, the elven trickster god, inspired the druid Fara Greenwood to breed a new version of mage weed which increased the potency of arcane rituals performed under its influence. Initially the increase in power was modest, but once word got out, all the nearby mages sponsored a breeding program to increase the potency of the effect.
Not all ritual spells can be affected by mage weed and affected spells are often transformed beyond recognition under its influence. Divination spells in particular tend to turn into hallucinations. In extreme cases, these hallucinations may manifest physically and become dangerous, or draw those nearby into an alternate reality until the effects of the weed wear off.
Lower level mages who try to use mage weed are often overcome, becoming both addicted to the weed and unable to perform even the simplest of magics.
Some non-ritual spells are also affected by mage weed. Fireball and other evocation spells are definitely affected, but so far none of the mages experimenting with them have survived the explosion that occurs on their first trial. As they say, the experiment was a success, but the experimenter died.
Undead appear unable to benefit from the use of mage weed.
The production and distribution of mage weed has been tightly controlled by the elves of the KKK (Kokanee Kootenai Kollectiv). They fear the wars that might result should it become widely available.