Update: According to Slate, the Mehlman Amicus Brief is being considered especially notable among the dozens of other briefs that have been filed.  The reason? The brief is signed by 303 conservatives, many of whom have previously opposed gay marriage, and includes notable signers like Senators Susan Collins and Mark Kirk, Massachusetts Governor Charlie Baker, former Pennsylvania Governor Tom Ridge, and retired General Stanley McChrystal.

On Thursday, according to TIME, a friend of the court brief was filed with the Supreme Court that contained more than 300 signatures from veteran Republican lawmakers and consultants.  This brief was organized by Ken Mehlman and concerns the April 28th cases that the Supreme Court will be hearing on the issue of same-sex marriage.

Depending on how the court rules, and it is expected that the court will rule by the end of June, these cases could legalize same-sex unions on a nationwide basis.

Signatories to the brief include current and former governors, current and former Republican members of the House of Representatives and Senate, among others.  This effort is similar to another effort in 2013, where Ken Mehlman organized another amicus brief for the Supreme Court case that overturned California’s Proposition 8.  That brief gathered 131 signatures from prominent Republicans.

According to TIME, the brief makes a conservative case for the court to strike down same-sex marriage bans, and states that the laws that “bar same-sex couples from the institution of civil marriage” are “inconsistent with the United States Constitution’s dual promises of equal protection and due process.”