Some medical marijuana caregivers have gone from taking cash for cannabis to bartering cell phones, concert tickets, even cars for medical pot.The trend is evident on websites such as Craigslist and cannabarter.com.In one ad, a poster who is identified as a licensed medical marijuana patient offers a weight bench in exchange for medical marijuana. Another ad, posted by someone claiming to be a licensed caregiver reads: You need medical marijuana, I need a riding lawn mower, and offers to trade medical pot to a licensed patient willing to give up a mower.Theres no limit right now to the creativity, said Matt Brown, executive director of Coloradans for Medical Marijuana Regulation.Brown said many caregivers who turn to bartering are looking to stay in compliance with a series of complex new regulations, which restrict a caregivers ability to turn a profit.It's an easy way to say, This is a straight barter, so I'm not making any money, said Brown.Brown said the downside of bartering is that it is unclear whether it is legal under Colorado law. Brown said Amendment 20, which legalized medical marijuana, protects transactions between patients and caregivers, but goes no further.Amendment 20 is silent on how the payment for that transaction goes, said Brown.Amendment 20 is also silent on whether different strains of medical marijuana can be exchanged between patients, but that has not stopped websites such as Strain Exchange, which connect patients who are looking to swap strains.Brown said the postings fall into a gray area of the law. New regulations require that caregivers treat a maximum of only five patients. But it would be difficult, if not impossible for law enforcement officials to determine whether the posters were bartering with more than five patients.Brown said because the law is vague, both patients and caregivers who participate in bartering, are opening themselves up to possible legal trouble.I think they're probably taking a bit more risk than many of them realize, said Brown. They are opening themselves up to the chance that they may still run into law enforcement that also doesn't understand those rules.