It is said that William Brennan, the great US supreme court justice, liked to greet his incoming law clerks with a bracingly simple definition of constitutional doctrine: five votes. “You can’t do anything around here,” Brennan would say, wiggling the fingers of his hand, “without five votes”.

Five votes. Five votes will presumably frame the court’s ruling in a trio of crucial employment-discrimination cases that were argued before the justices on Tuesday. All three cases focus on the scope of protections provided by Title VII of the Civil Rights Act of 1964, which bars workplace discrimination “because of … sex”. Does such a bar prevent discrimination on the basis of sexual orientation? That is the question raised by the first two cases, Bostock v Clayton and Altitude Express v Zarda, while the third, Harris Funeral Homes v EEOC, asks whether Title VII’s bar also covers discrimination against transgender people.

In its landmark ruling in Obergefell v Hodges (2015), the court recognized a right to gay marriage, but that was a different supreme court. Justice Anthony Kennedy, who long served as the swing vote in a closely divided court, wrote the majority opinion in Obergefell. Kennedy has since been replaced by Brett Kavanaugh, and whatever else one might think of the court’s junior-most justice, he will undeniably move the court firmly to the right. Indeed, this supreme court is the most conservative that the US has seen since the early years of FDR’s presidency, when a hidebound supreme court aggressively struck down New Deal laws designed to alleviate the economic suffering of millions.

That same hidebound spirit was put richly on display yesterday when Justice Samuel Alito observed during arguments that were the court to extend Title VII protections to gay people, it would be “acting exactly like a legislature”. Such a move, Alito fretted, would “change the meaning of what Congress understood sex to be”. The argument is less wrong than it is tiresome. Scanning the intent of a Congress is a notoriously unreliable guide to statutory interpretation and one that conservatives generally abjure. Should Congress object to the court’s extending the Civil Right Act’s protections to LGBTQ people, it could always act to curtail the court’s reading.

More to the point, Alito’s observation is less an explanation than a rhetorical ploy. Every law student solemnly learns that interpreting the law is the province of the courts while making law is the precinct of legislature – only then to learn that the distinction is utterly unstable and largely incoherent. Conservative jurists call results they like – for example, that the second amendment protects a personal right to gun ownership – interpretations. Results they don’t like – extending basic workplace rights to gay and transgender persons – are acts of lawmaking, a usurpation of proper judicial function.

Granted: it is not a foregone conclusion that the court’s conservative bloc will refuse to extend the protections of the Civil Rights Act to LGBTQ people. Hopeful was Justice Neil Gorsuch’s observation that sex, the operative term in Title VII, appeared to be a “contributing cause” in the firing of transgender petitioners. Less encouraging was his observation that an extension of protections might cause “massive social upheaval” – with the understanding that triggering such upheaval should be left to Congress and not the court.

So safe money counts five votes refusing to extend workplace protections to millions of LGBTQ people. That Gorsuch appears to be the swing vote here is all the more regrettable. Justice Gorsuch, of course, is not to blame for his position on the court. That falls to Mitch McConnell, who cynically stole a seat that rightfully belonged to Merrick Garland. McConnell’s constitutional coup d’état will leave all the decisions of this five-person bloc smacking of illegitimacy. Particularly those with Gorsuch’s stamp.