The federal government, once again, is seeking to establish its relevance by acting outside its Constitutional authority to dictate to the States. Federal DEA raids and letters written by U.S. Attorney Genitals are the next step in their continued attack on states rights and the rights of the people to be “secure in their persons.” The key graph from StopTheDrugWar.org:

…and the federal government has unveiled an ominous new weapon in its war on the weed: US attorneys in a number of medical marijuana states sending letters to politicians threatening dire consequences, even the potential arrest of state employees, if states okay schemes to tolerate and regulate medical marijuana distribution.

http://stopthedrugwar.org/chronicle/2011/may/05/feds_new_medical_marijuana_offe

According to StopTheDrugWar.org, Medical marijuana officials in these states have been threatened, including elected officials and governors.
Here is a partial list of the states and more information about each.

• Arizona: (see the article Arizona Medical Marijuana and Prop 203)
• California (see the article California Medical Marijuana and Proposition 215, the Compassionate Use Act of 1996)
• Colorado (Colorado MMJ and Amendment 20)
• Hawaii (Hawaii Medical Marijuana and SB 862 HD1)
• Montana (Montana MMJ and Initiative 148)
• Rhode Island
• Washington