Fourth, it must be shown that a tied selling agreement significantly restricts trade. Evidence of anti-competitive effects includes unreasonably high prices for tied products and unreasonably low prices for competing products in a captive market. An applicant is not required to prove that an undertaking has actually controlled prices by means of a tying agreement, as is necessary to establish certain monopolistic practices, but only that prices and other market conditions have been significantly influenced. The guidelines on enforcement priorities referred to in Article 102 set out the circumstances in which measures should be taken against tied selling practices. First of all, it is necessary to determine whether the undertaking being sued holds a dominant position on the binding or binding market. The next step is then to determine whether the dominant undertaking has linked two different products. This is important because two identical products cannot be considered related under Article 102(2)(d) of the formulation, which states that products are considered to be related if they do not contain compounds “by reason of their nature or commercial use”. This leads to problems in the legal definition of what amounts to a link in the scenarios of selling cars with tires or selling a car with radio. Therefore, the Commission provides guidance on this issue, building on the Microsoft judgment, and notes that “two products are distinct if, without coupling or bundling, a significant number of customers would purchase or purchase the tied product without also purchasing the tied product from the same supplier, thus allowing independent production for both the tied product and the tied product”.
The next question is whether the customer was compelled to purchase both the tying and the tying products, as suggested by Article 102(2)(d): `make the conclusion of contracts subject to the acceptance of additional obligations by the other parties`. In situations where contractual provisions are established, it is clear that the criterion will be met; For an example of a non-contractual ty, see Microsoft. In addition, the question of whether the company can have a lock-in effect applies to an enterprise.  Ibm , Eurofix-Bauco v. Hilti , Telemarketing v CTC , British Sugar and Microsoft are some examples of tied selling practices with an anti-competitive foreclosure effect. Subsequently, the dominant undertaking may argue that it may provide that tying is objectively justified or increases efficiency and that the Commission is prepared to examine that claims which constitute binding agreements may lead to economic efficiency of production or distribution that benefits consumers.  A typical tying agreement occurs when a seller with market power for a product (the “ty item”) requires that each customer who purchases that item also purchase a second item (the “linked” item). The market for the linked item is usually very competitive and the seller uses their market power for the first item (the “ty item”) to increase sales in the competitive market for the second item. Although the above explanation refers to products, tied selling agreements may include goods or services. In a typical tied selling agreement, a company sells a product or service to a buyer that is explicitly or implicitly linked to the purchase of another product or service from the same seller. For example, a company can set up a walled garden or closed platform where a smart device is sold and apps, media, and other content can only be purchased through the smart device provider. In the past, Microsoft and Apple have been accused of making deals.
Another important case involving a tied sale action was United States v. Microsoft.  Microsoft is reported to connect Microsoft Windows, Internet Explorer, Windows Media Player, Outlook Express, and Microsoft Office. The United States argued that the bundling of Internet Explorer (IE) on the sale of Windows 98, which made it difficult to remove IE from Windows 98 (para. B example, not on the “Remove Programs” list) and the manufacture of Windows 98 to work “unpleasantly” with Netscape Navigator, was an illegal link between Windows 98 and IE.  Microsoft`s counter-argument was that a web browser and mail reader were simply part of an operating system included in other PC operating systems and that product integration was technologically justified. Just as the definition of a car has changed to include things that were previously separate products, such as speedometers and radios, Microsoft has claimed that the definition of an operating system has changed to include their previously separate products. The U.S. Court of Appeals for the District of Columbia Circuit rejected Microsoft`s claim that Internet Explorer was only one facet of its operating system, but the court ruled that the connection between Windows and Internet Explorer should be analyzed respectfully according to the rule of reason.  The U.S. government`s claim was settled before a final solution was found. Classifying an antitrust complaint as a violation of antitrust law per se is important because the plaintiff does not have to prove anti-competitive harm, since the law assumes that antitrust violations per se cause anti-competitive harm without redeeming the competitive value.
By themselves, antitrust violations are generally limited to price fixing, market allocations, tendering, group boycotts (in some cases) and, as explained here, certain forms of linkage. For competitive purposes, a monopolist may use mandatory purchases or “tied selling” to make sales in other markets where it is not dominant and to make it more difficult for competitors to sell in those markets. This can limit consumer choice for buyers who want to buy a product (“constraining”) by forcing them to buy a second (“linked”) product as well. As a general rule, the “tied” product may be a less desirable product that the buyer cannot purchase unless necessary, or it is possible to obtain it from another seller. If the seller offering the related products has sufficient market power over the “binding product”, these agreements may violate antitrust law. One of the effects of linkages may be that lower quality products achieve a higher market share than would otherwise be the case. Example: The FTC challenged a drug manufacturer that required patients to purchase its blood monitoring services as well as its drugs used to treat schizophrenia. The manufacturer of the drug was the sole manufacturer of the drug, but many companies were able to offer blood monitoring services to patients who were using the drug. The FTC claimed that tying the drug and monitoring services increased the price of this medical treatment and prevented independent providers from monitoring patients taking the drug.