Cities can tell you where you can and can’t park, and they can decide which areas of town are zoned for which types of commercial uses, but can a city determine where a food truck can park based solely on the type of food it makes?

Baltimore City Code Article 15, Section 17-33 sets a controversial restriction on where food trucks and other mobile vendors can do their business in the city, declaring that “A mobile vendor may not park a vendor truck within 300 feet of any retail business establishment that is primarily engaged in selling the same type of food product, other merchandise, or service as that offered by the mobile vendor.”

So if you’re a hamburger truck, you’ve got to park at least 100 yards away from a McDonald’s or any other established eatery known for selling burgers. However, if you’re selling tacos from your food truck, that 300-foot rule wouldn’t keep you from parking near a burger joint, though it arguably might if one of those bricks-and-mortar restaurants decided to add tacos to the menu.

At the same time, nothing in the Baltimore city code would prevent you from opening a bricks-and-mortar taqueria next to an existing taco shop, or a burger joint across the street from a McDonald’s. To food truck operators, this seems unfair.

A lawsuit filed today by two Maryland food truck operators challenges the legality of the Baltimore ordinance, claiming that the 300-foot rule violates their rights to equal protection and due process under the state’s constitution.

“The 300-foot rule has only one, illegitimate purpose: to protect existing brick-and-mortar businesses from competition,” reads the complaint [PDF], which contends that the ordinance fails to address any legitimate government interest.

The plaintiffs each operate their own food truck, one selling pizza and the other selling barbecue. The owner of the pizza truck says he is unable to do business “in large parts of the city” because his menu overlaps too closely with the food sold at pizzerias and Italian restaurants throughout Baltimore.

The lawsuit alleges that Baltimore police are often called by restaurants to enforce the 300-foot rule, but that “it is often unclear whether the truck is actually within 300 feet” of a restaurant selling similar food.

The complaint gives an example from May 2015, when the pizza truck owner claims that two police officers told him he needed to move his truck, alleging that he was in violation of the 300-foot rule. It wasn’t until after he demanded proof of any nearby restaurants selling pizza — and after the officers conferred with their colleagues over the radio — that he was allowed to continue operating.

Had he been cited for a violation, he would have faced a fine of $500. Three violations in a year can result in a vendor’s license being revoked.

The barbecue truck only operates occasionally within the Baltimore city limits, obtaining a temporary license as needed. She says she has applied for a permanent license from the city and wants to park more regularly in Baltimore, but that she “intends to refrain from regularly doing business in Baltimore until the 300-foot rule is eliminated because it would preclude her from operating in large swaths of the city, particularly those locations best for attracting potential customers.”

“The rule creates a discriminatory classification that penalizes Plaintiffs based entirely on whether they are within 300 feet of a brick-and-mortar business that primarily sells the same type of food,” argues the lawsuit. “The City’s police power does not extend to engaging in economic protectionism to benefit brick-and-mortar establishments at the expense of mobile vendors, including food trucks, for no reason other than to protect the former from competition by the latter.”

The lawsuit asks the court to rule that the 300-foot rule is unconstitutional, and for an injunction barring the city from enforcing it.

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.