As of the New Year, Iowans can go just over the Mississippi River into neighboring Illinois to buy recreational marijuana. Now that sales are legal in the Prairie State, some officials in Iowa are warning residents to be mindful of state law.

Despite the law change in Illinois, it is still illegal to transport the drug across state lines or to drive impaired.

Sergeant Alex Dinkla of the Iowa State Patrol says officers will likely be keeping an eye out for potentially impaired drivers, especially in the eastern part of the state.

“There’s gonna be probably a little extra awareness on that side of the state as they are working," he said. "But as the state as a whole, we take a very strong stance against it that, if you have any marijuana in your vehicle, on your person, you will be charged with that.”

A bridge from Illinois leads right into downtown Dubuque and County Sheriff Joe Kennedy says his deputies are well aware of the changes across the river.

“We just want people to understand, when they go over to Illinois and they buy it, even if they may buy it legally over there, as soon as they cross the state line it is no longer legal and we are going to enforce it as such,” Kennedy said.

The marijuana legal landscape is changing across the Midwest and Mountain West. Iowa has approved limited access to medical marijuana for certain qualified patients. Meanwhile, in Michigan, Illinois and Colorado the substance is now fully legal.

Despite the patchwork of regulations in the region, Kennedy says residents should be aware of Iowa law.

"Our deputies have stopped people from say, Colorado. And we stop them and the deputy detects marijuana in the vehicle or we get a canine or whatever, and end up finding marijuana in the vehicle. And the first thing they say is, 'well, it's legal in Colorado," he said. "Well, that's fine, but you're not in Colorado."

When it comes to driving under the influence, it can be difficult to test for marijuana impairment because of how the drug stays in a person’s system. According to the National Conference of State Legislatures, there’s no national standard for drugged driving like there is for drunk driving.