DETROIT, MI - What would it take to get the Koch brothers and the Sierra Club to stand beneath the same tent?

The answer is purported anti-consumer laws affecting Tesla Motors, a California-based electric carmaker that has its direct-to-consumer sales outlawed in Michigan and elsewhere.

The Koch brothers' Americans for Prosperity conservative political advocacy group and environmental protection group the Sierra Club have signed a letter decrying the "anti-consumer effects" of laws barring direct vehicle sales in states like Michigan.

Acknowledging their broad range of public interests, the signatories of the letter, listed below, note they frequently find themselves on different sides of policy debates.

"However, we now find common ground on an issue of considerable public importance concerning state laws that restrict the purchase and sale of automobiles," states the letter, released Tuesday. "In short, we oppose efforts by state legislatures or regulatory commissions to forbid car manufacturers from opening their own stores or service centers in order to deal directly with consumers."

In October, Gov. Rick Snyder signed a bill his office described as bipartisan legislation that simply strengthens existing law as it pertains to automobile dealership sales in Michigan.

But Tesla's legal team argued the bill - HB 5606 - is a direct effort at shutting the company and its unique, direct-to-consumer sales model out of Michigan.

The bill was approved 38-0 in the Senate and 106-1 in the House of Representatives after being presented to state legislators as aimed at prohibiting car dealerships in the state from dictating fees they charge customers. With the legislation, dealerships can decide whether or not to charge certain transaction fees.

"This bill does not, as some have claimed, prevent auto manufacturers from selling automobiles directly to consumers at retail in Michigan - because this is already prohibited under Michigan law," Snyder said in a letter to lawmakers that accompanies the signed bill.

Todd Maron, general counsel for Tesla, said at the time that not only does it further ensure that company cannot sell directly to consumers in the state, it goes so far as to prohibit Tesla from displaying its cars to and communicating with potential customers in Michigan.

Tesla has also run into what some see as dealership-backed laws preventing its direct-to-consumer sales in places such as Texas, Arizona, New Jersey, and to some degree, Maryland, too.

"At the time these laws were passed many decades ago, the car dealers argued that manufacturers should not be allowed to compete directly with their own franchised dealers, since they might then be able unfairly to undercut their dealers on price," Tuesday's letter reads. "However valid these concerns may or may not have been at a time when the 'Big Three' manufacturers dominated the market, it is important that the law keep up with the changes that have occurred in the automobile market today."

General Motors for its part released a statement shortly after the bill was signed, throwing its support behind it.

"We believe that House Bill 5606 will help ensure that all automotive manufacturers follow the same rules to operate in the State of Michigan; therefore, we encourage Governor Snyder to sign it," read GM's one-sentence statement, posted to its media webpage.

The letter from Tuesday goes on to say that the group's concerns are not limited to just Tesla, but apply also to other companies seeking to distribute their cars directly to consumers - something the signatories argue could reduce costs and increase consumer satisfaction. The group argues that laws preventing direct-to-consumer sales "retard innovation."

The coalition was brought together with the help of University of Michigan law professor Daniel Crane, who specializes in anti-trust laws.

The letter is signed by American Antitrust Institute, Americans for Prosperity, Consumer Federation of America, Consumer Action, Consumers for Auto Reliability and Safety ("C.A.R.S."), Institute for Justice, The Information Technology & Innovation Foundation, Mackinac Center, Sierra Club - National and Environment America with chapters from 28 states, including Michigan.

David Muller is the automotive and business reporter for MLive Media Group in Detroit. Email him at dmuller@mlive.com or follow him on Twitter