The first shot was fired by the City of Seattle last year when it passed an ordinance intended to assist with the unionization of ride-sharing drivers. The ordinance was groundbreaking in that it is the first of its kind in the country. The ordinance was also seen as controversial because it remains to be seen whether such a regulation could comply with national labor laws. The U.S. Chamber of Commerce tried to join the fight by filing a lawsuit against the City, claiming the ordinance violated antitrust and labor laws. But a federal judge dismissed that lawsuit by concluding that the Chamber didn’t have standing to pursue the claims, and even if it did, that no damage had yet been done and so the lawsuit was premature.

The rules just went into effect on Tuesday of this week (January 17), and Uber didn’t waste any time firing the next shot in this battle. The ride-sharing giant just filed a lawsuit in King County Superior Court seeking to block the rules and scrap them altogether. At this point in time, the lawsuit isn’t attacking the underlying validity of the ordinance itself. Instead, Uber is arguing that the rule-making process that led to the ordinance was flawed, contending that those opposed to the efforts weren’t provided a meaningful opportunity to offer comments. However, no matter how this particular conflict is resolved, it seems reasonable to assume that the legality of the ordinance itself will be challenged in court by somebody sometime soon.