In 2018, two of the biggest tech companies in the world signed an agreement creating an official storefront for Apple on Amazon's website, in an attempt to reassure customers that the products sold there were genuine. As part of the agreement, any third-party retailer not certified as an Apple Authorized Reseller was prohibited from selling Apple products on Amazon Marketplace.

The latter part of the arrangement proved controversial, and has now led to Spain's competition authority (Comisión Nacional De Los Mercados Y La Competencia, or CNMC) initiating a preliminary investigation against the two companies "for possible anti-competitive practices", reports 9to5Mac.

In a press release the CNMC says it "has had access to certain information" indicating that the companies could be in violation of both Spanish competition law and EU law. The companies are alleged to have prevented retailers from freely marketing and selling Apple products, restricting competition.

"Specifically, the possible illegal conduct would consist of an agreement between both groups that would include possible restrictions on the Amazon website in Spain in relation to: (i) The retail sale of Apple products by third parties; (ii) Certain advertising of competing Apple products and certain campaigns directed at Apple customers by Amazon; (iii) Other commercial restrictions," says the CNMC (via Google Translate).

"The investigated conduct could be restricting competition in the sectors of the Internet sale of electronic products, and the provision of marketing services to third-party retailers through online platforms (Marketplace) in Spain."

The CNMC has 18 months to bring charges. The Amazon Marketplace clause of the agreement is already the subject of antitrust investigations in both the US and Italy.

This article originally appeared on Macworld Sweden. Translation and additional reporting by David Price.