[semimojo]

My understanding of the Constitution is that the power to select electors resides with the legislature.

Note that their plan is to introduce legislation.

Legislation in PA requires the governor's signature before it becomes law.

[Savage Rider]

No, they don’t need “legislation” or a “law” to take back the power they designated to the SOS. Their power to do this resides in the US Constitution and cannot be abridged.

[Svartalfiar]

Legislation in PA requires the governor's signature before it becomes law.

This isn't lawmaking, it's the legislature fulfilling Constitutional duties. PA may not recognize it as law, but on the Federal side it's recognized and Constitutionally legal.