TIMONIUM, Md. (WJZ) — One of President Barack Obama’s new gun control proposals–a ban on high-capacity magazines–is already state law here in Maryland, but that didn’t stop two men from trying to sell those magazines illegally at a gun show in Timonium last weekend.

Mike Schuh explains how officers say they caught them in the act.

Police say the sale of the magazines was no accident.

High-powered rifles like the AR-15 are popular among gun owners, but in the state of Maryland, it’s illegal to sell or own magazines for the rifles with the capacity of storing more than 20 rounds of ammunition. Critics of the high-capacity magazines believe they allow lawbreakers to carry out acts of mass violence.

Baltimore County police say that law was recently broken at a gun show in Timonium.

“The magazines were labeled 20-round magazines but were, in fact, 30-round magazines,” said Detective Cathy Batton, Baltimore County Police.

Police say it happened Jan. 11. Undercover detectives with the Firearms Interdiction Team saw a customer purchase a high-capacity magazines from a vendor. Police say those detectives went back to the vendor to try and do the same.

“The undercover detective asked to purchase the 30-round magazine. He specifically asked for a 30-round magazine. The vendor replied that he was in Maryland so he couldn’t say it was a 30-round magazine but that the detective would be able to purchase what he was looking for,” Batton said.

Police arrested 64-year-old Richard Summers of Waldorf and 57-year-old John Heilmeier of Cumberland, Va.

Others are critical of past control policies.

“Nothing that they’ve done in the past has seemed to have any kind of positive effect on criminal use of firearms,” said gun owner Michael Horst.

Baltimore County Police Chief Jim Johnson has been working with state lawmakers in restricting high-capacity magazines in order to reduce gun violence.