Samsung has one of the most unique, and downright odd relationships with Microsoft any tech company possibly could. A recent court filing suggests that the Microsoft acquisition of Nokia creates antitrust issues that impact the ability for the two to continue working together.

Usually people don’t automatically think of the two as collaborative, but actually, they are. At least on certain Windows phones that Microsoft agreed to work with Samsung on. The filing is actually the result of an earlier filing on behalf of Microsoft, which alleges that Samsung failed to follow through on a couple of the key terms to their agreement.

According to Microsoft, Samsung still owes $6.9 million in royalties stemming from more than $1 billion that it has been delaying paying. However, Samsung fired back noting that Nokia being acquired by Microsoft violates the deal the duo made in 2011.

Their original deal was complex, but was an exchange of the sorts. The original deal from 2011 stated that Samsung would pay Microsoft royalties for a patent license that would cover Samsung’s Android phones. At the same time, Samsung agreed that they would help develop Windows phones and share what was classified as confidential business information that the company considered worthy of protection from the likes of Nokia.

In other words, Samsung did not want to collaborate with Nokia – who they compete with on the Android market. That being said, if Samsung met a sales goal for the Windows devices that they were developing, they would have the opportunity to get their royalties payment reduced.

They did not make their goal, and did not take anything away from the iPhone market share, and that was the ultimate issue with the agreement. The filing goes on to point out that once Microsoft acquired Nokia they become direct hardware competitors and that would essentially nullify their agreement, or at least void it out.

Samsung goes on to point out that from their perspective, it could invite future “charges of collusion” if the two competitors are in an agreement as they previously were, and that their motivation is to avoid future charges against them, rather than avoidance of paying royalties.

Both Samsung and Microsoft have said that they believe their cases are strong, and have expressed confidence in winning in court.