Clark County is moving toward a ban on collective medical marijuana gardens.Commissioners Marc Boldt and Tom Mielke both instructed county staff at a Wednesday morning workshop meeting to begin work on a policy that would prohibit the gardens as an acceptable land use in the county. Commissioner Steve Stuart was absent from the meeting.The gardens allow medical marijuana growers to establish community gardens where as many as 10 patients can grow up to 45 plants. The state approved the gardens last year, but the county placed a moratorium on them until June 2013 to come up with an implementation plan.Boldt and Mielke both said they are concerned that allowing the gardens would fly in the face of federal law, which prohibits marijuana use, sale and cultivation. Commissioners also said they would prefer to wait and see how the federal government handles voter-approved Initiative 502, which will allow adults older than 21 to use recreational marijuana.“We took an oath to uphold the federal law, too,” Mielke said. “I think there are too many unanswered questions here. For us to move forward (on allowing zoning) would be premature.”Commissioners also referenced a letter the county received from the federal Drug Enforcement Agency as a reason for their decision. That letter said if the county were to be involved in the permitting or regulation of such gardens, it could be in violation of federal law.