It is settled law that public employees who do not belong to the union that represents them cannot be required to pay fees that the union would use for political activity like union organizing. But in 1977, the Supreme Court ruled that public employees who do not belong to a union can be required to pay a fee – often known as a “fair share” or “agency” fee – to cover the union’s costs to negotiate a contract that applies to all public employees, including those who are not union members. That decision, in Abood v. Detroit Board of Education, turned 40 last month. But if an Illinois state employee, Mark Janus, has his way, Abood may not survive to see 41. Yesterday Janus asked the Supreme Court to overrule that decision and hold that requiring an unwilling employee to pay even this more limited fee violates the First Amendment. If the court agrees to weigh in, as it is likely to do, its ruling could affect not only the financial health of public-employee unions, but possibly even politics more broadly. And its decision could also be one of the first tangible and significant signs of the impact of the 2016 presidential election on the Supreme Court.

For eight of the nine justices, the issue is a familiar one. It first came before them three years ago, in another case from Illinois. But the court didn’t rule on the question then; instead, it concluded that the employees in that case – home health aides, who usually take care of family members and were compensated by the state – were not actually public employees. However, five justices – Justice Samuel Alito, whose opinion for the court was joined by Chief Justice John Roberts and Justices Antonin Scalia, Anthony Kennedy and Clarence Thomas – suggested that they might be willing to reconsider Abood.

Two years later, the issue was back, this time in a challenge filed by a group of California public-school teachers who objected to having to pay agency fees. The court heard oral argument in the case on January 11, 2016, but had not yet announced its decision before Justice Antonin Scalia died just over a month later. On March 29 of last year, the remaining eight justices revealed that they were deadlocked, issuing a one-sentence order that left the lower court’s ruling in favor of the union in place. The teachers asked the court to reconsider that ruling, but – after repeatedly putting off action on the request – it declined to do so.

With Justice Neil Gorsuch now on the bench, however, Janus hopes that the Supreme Court will seize its third opportunity to reverse Abood. The U.S. Court of Appeals for the 7th Circuit rejected Janus’ argument that requiring him to pay an agency fee violated his rights under the First Amendment, explaining that it did not have the power to overrule Abood. But the Supreme Court does have that power, and yesterday Janus asked the justices to step in. He argues that, because issues like salaries, pensions and benefits for government employees are inherently political, agency fees – even if characterized as the costs of contract negotiations – are supporting “speech designed to influence governmental policies.” Therefore, he maintains, requiring him to pay an agency fee isn’t actually any different from forcing him to subsidize a group that lobbies the government. Indeed, he observes, an agency fee may require state employees to “subsidize advocacy that they oppose and that may harm their interests. This is perverse, akin to requiring kidnapping victims to pay their captors for room and board.”

The stakes in this case are high, not only for the parties but also for any other union that represents public employees who must pay agency fees. If employees are not required to pay the fees, many of them probably won’t, which would have a direct effect on the financial health of public-employee unions. And although the fees now at issue before the court cannot be used for politics and lobbying, that could in turn lead to a reduced role on the political stage for organized labor, which by one estimate spent $1.7 billion during the 2012 election cycle.

The respondents in the case, the state of Illinois and the union that represents Janus, have 30 days to file their response to Janus’ petition for review. The justices will almost certainly not consider the petition until late September, when they return from their summer recess. If they were to grant review then, the case would likely be argued in early 2018, with a decision before the end of next June.