A Colorado sporting goods store is closing after refusing to sell Nike merchandise in a protest against the company’s endorsement deal with former NFL player Colin Kaepernick.

Prime Time Sports, which had been in business for more than 20 years, decided to pull Nike products from its shelves after the company’s deal with Kaepernick to be the face of Nike’s 30th anniversary “Just Do It” advertising.

Owner Stephen Martin said his business struggled after the decision, and “just can’t keep the doors open anymore.”

“Being a sports store without Nike is kind of like being a milk store without milk or a gas station without gas. How do you do it? They have a monopoly on jerseys,” Martin told a local NBC station.

Kaepernick sparked a wave of protests by fellow NFL players in 2016 when he began kneeling during the national anthem to protest police brutality and racial inequality.

Nike’s decision to feature Kaepernick in the ads was immediately controversial, with some customers boycotting the brand and even burning their merchandise. President Donald Trump and his conservative backers lashed out at the NFL protests, and Trump attacked Nike for featuring Kaepernick.