Editor’s note: The following is the fourth of a multi-part series on methamphetamine.COLUMBIA CITY — Law enforcement officials are facing a difficult challenge when it comes to methamphetamine — how do you police a drug that is made of household items?While other drugs, such as marijuana and cocaine, are easy to determine guilt, Whitley County Drug Task Force Detective Bill Brice said the law can be tricky with meth.Lawmakers have put a limit on the amount of pseudoephedrine that can be purchased per day and per month.Pseudoephedrine is the main ingredient in the meth-making process, but it is also used in cold medicine, commonly known as Sudafed.A person is allowed to buy 3.6 grams of pseudoephedrine per day, and up to nine grams per month.Brice said the limitations can be tricky for large families.“Let’s say you’re the mom of a family of five. You’re sick, your husband is sick and all the kids are sick. So you’re going to go out and buy enough medicine for the family — which could actually be breaking the law,” Brice said. “We’ve had that happen. But we just have to look at the circumstances and see if it happens again.”To read the rest of this story, see the April 8 issue of The Post and Mail. Don't have a subscription? Call (260) 244-5153 or subscribe to our e-edition. For breaking news, sports updates and additional coverage, bookmark the homepage and find us on facebook and twitter.