Two artists' projects in Texas have run afoul of that state's Transportation Code and been deemed illegal.

This summer, the Texas Department of Transportation (DOT)  pronounced artist Richard Phillips's latest work, an outdoor roadside sculpture near Marfa, Tex., and commissioned by Playboy Enterprises, to be unlawful advertising and ordered the company to remove it. Close by is Prada Marfa (2005), a site-specific Land art project by Scandinavian artist duo Elmgreen & Dragset, which the DOT has also deemed illegal.

Phillips's Playboy Marfa (2013) comprises a 1972 Dodge Charger atop a box in front of a 40-foot-tall neon Playboy bunny logo. Texas's Transportation Code regulates outdoor advertising, which includes signage with logos. Located along a barren stretch of Highway 90, Prada Marfa is a faux-storefront emblazoned with the Prada insignia (the company's founder, Miuccia Prada, gave permission). It does no retail business and was commissioned not by Prada (although Miuccia Prada selected and donated the "historical display" of shoes and bags in the faux-store), but by the New York nonprofit Art Production Fund in collaboration with Texas nonprofit Ballroom Marfa.

Their work is not an advertisement, Elmgreen & Dragset said on Friday in a statement issued via Ballroom Marfa. The duo says it came as "a big surprise" that the department "now, after eight years, may declare this well-known artwork to be illegal" and that it "would be a shame for the local community if it disappeared . . . since the work is one of the strong points for cultural tourism, which is such an important financial factor in the region."

The artists assert that "the right definition of advertisement must be based on criteria more accurate than just including . . . a logo."

Department of Transportation spokeswoman Veronica Beyer told A.i.A. by e-mail Monday that "Prada Marfa is considered outdoor advertising." For that reason, she said, "a state outdoor advertising license and permit are required." She added, "We appreciate artwork and enjoy seeing it across our state, but like all other outdoor signs, people responsible must follow state and federal laws."