Sherman gets some of its water from Lake Texoma - which is infested with zebra mussels - an invasive species.
The federal Lacey Act bans transporting invasive species across state lines.
The state border in Lake Texoma was officially determined in 2000 - and cuts across the pumping facility, placing most of the pumps in Oklahoma.
Now, some are questioning whether the Greater Texoma Utility Authority is breaking the law.
But GTUA General Manager Jerry Chapman said zebra mussels are already in Texas.
"Bear in mind, when zebra mussels were discovered in Lake Texoma in 2009, they were already in the Red River Basin," he said.
The Red River basin includes Grayson County.
Sherman Mayor Bill Magers said determining the border is an arbitrary argument.
"When you consider that Texas owns 50 percent of the water in Lake Texoma, it becomes comical when you try to decide what 50 percent of the water that is," he said.
Magers said water from Lake Texoma is pumped straight into a treatment plant, which kills any lingering zebra mussels.
"The Lacey Act is designed to keep you from taking critters from point A to point B," he said. "It is not designed to talk about pumping water from a Lake or body of water into a municipal water system that is treating that water."
Chapman said GTUA has always been in full compliance with federal authorities.
"We have never had anything to hide. We have keep in contact with the Corps of Engineers, with the U.S. Wildlife and Fisheries, over the period of time since the time the zebra mussels were discovered," he said. "They know of our activities. They have not indicated we should stop pumping."
Magers agrees they are following all laws.
"We bought our water from the Corps of Engineers, a federal government agency," he said. "We have been permitted by the state and U.S. governments. This idea that we're not playing by the rules is absolutely ridiculous."
The North Texas Municipal Water District told us they stopped pumping when zebra mussels were discovered because they don't have a closed system - which would filter out zebra mussels - but they are currently building the necessary facilities.