The primary day of a weeklong listening to that would decide the result of Microsoft’s $70 billion acquisition of the online game big Activision Blizzard opened Thursday with a promise from Microsoft: If a federal decide grants an injunction that might delay the deal’s closing, Microsoft may abandon the deal altogether.

“That is going to resolve whether or not the deal goes ahead,” stated Beth Wilkinson, Microsoft’s lead lawyer. She added {that a} loss may power the corporate right into a “three-year administrative nightmare” that might sink the transaction, which it hopes to shut by July 18.

That set the stakes for the listening to in U.S. District Courtroom in San Francisco, the place the Federal Commerce Fee started laying out its case that Microsoft’s acquisition of Activision — and its fashionable video games like Name of Obligation — could be devastating for the online game trade.

The F.T.C. is asking Choose Jacqueline Scott Corley for a preliminary injunction, which might bar Microsoft from finishing the deal earlier than the F.T.C. had the possibility to argue the case in its inside courtroom.

The conflict is broadly seen as a take a look at of whether or not current efforts to extra aggressively curb the facility of tech giants around the globe will succeed. Lina Khan, the chair of the F.T.C., has argued that huge tech firms have huge affect over on-line commerce and communication, permitting them to interact in anticompetitive practices that hurt shoppers.

“If this deal is accomplished, the mixed firm may have and is more likely to have the power and incentive to hurt competitors in numerous markets associated to consoles, subscription companies and cloud,” James Weingarten, the F.T.C.’s lead lawyer, stated in courtroom on Thursday.

Mr. Weingarten stated Microsoft may make Activision’s video games unique to its Xbox console, or degrade their high quality on different platforms to make the Xbox extra interesting to avid gamers. He pointed to Microsoft’s $7.5 billion buy of ZeniMax Media and its slate of recreation studios in 2020, after which Microsoft made a few of these video games unique to Xbox. The F.T.C. pointed to an settlement made between Disney and ZeniMax to supply a recreation about Indiana Jones for a number of consoles. After Microsoft purchased ZeniMax, the settlement was amended and the sport grew to become unique to Xbox. It was a sign, the F.T.C. seemed to be arguing, that Microsoft may make future Activision video games unique to Xbox, even amending current offers to take action.

The F.T.C. has argued that absorbing Activision’s video games into Microsoft’s portfolio would additionally give it an unfair edge within the nascent marketplace for cloud gaming.

Sony, which makes the rival PlayStation console, has been a vocal critic of the deal, and has stated that PlayStation avid gamers may lose entry to Name of Obligation — an infinite franchise that has earned greater than $30 billion in lifetime income — if Microsoft determined to make the sport unique to Xbox. Microsoft has denied that it will achieve this.

Microsoft stated the Activision deal would as a substitute be good for shoppers, increasing their capacity to play Activision’s video games by means of low-cost choices like Microsoft’s Xbox Recreation Cross, a subscription service, or by means of the platforms of different firms like Nintendo and Nvidia, with which it has struck offers.

Ms. Wilkinson additionally argued that it will be nonsensical for Microsoft to take away Name of Obligation and different titles from PlayStation as a result of the corporate would lose out on an enormous chunk of the sport’s income. She stated Sony had develop into the “complainer in chief” within the case, and confirmed an electronic mail from Sony’s chief govt, Jim Ryan, suggesting that he didn’t actually consider Microsoft would withhold Name of Obligation. Microsoft additionally pointed to its acquisition of Mojang, which produces Minecraft. It has continued to permit Minecraft to be accessible throughout platforms.

The F.T.C. has in one other lawsuit accused Meta, Fb’s guardian firm, of reducing off nascent opponents when it purchased Instagram and WhatsApp. On Wednesday, it sued Amazon over allegations that the corporate tricked customers into signing up for its Prime subscription service. However the F.T.C. has had setbacks: Its problem to Meta’s buy of a digital actuality start-up fell aside this 12 months after a decide declined to cease the deal from closing.

The F.T.C. initially challenged Microsoft’s bid for Activision utilizing an in-house courtroom. However that courtroom doesn’t have the authorized authority to cease the deal. The F.T.C. requested the federal courtroom to step on this month, saying it feared Microsoft would attempt to full the deal regardless of the authorized challenges.

The listening to in Choose Corley’s courtroom may very well be a decisive take a look at for the F.T.C. If Microsoft wins, it would sign that there are weaknesses within the F.T.C. case and will trigger the company to drop its problem to the deal. However a win for the F.T.C. could be an indication that its broader problem has legs, and will put new stress on Microsoft and Activision to rethink the multibillion-dollar company marriage.

Although most governments around the globe, together with the European Union, have authorized the acquisition, Microsoft was dealt a setback in April when a British regulatory authority blocked it. That call is underneath attraction.

The high-profile listing of witnesses anticipated to testify earlier than Choose Corley over the following week contains Satya Nadella, the chief govt of Microsoft, and Bobby Kotick, the chief govt of Activision. Mr. Ryan, the chief govt of Sony, will seem through a prerecorded video deposition.