> Textualism might give the court some useful definitions, but it is after all still called, quite literally, an opinion.

I don't think you understand SCOTUS' decision here. They are not banning TikTok. Congress is doing so (actually forcing a sale of TikTok or be banned). They are simply ruling whether Congress acted unconstitutionally by doing so. In other words, if they overrule Congress, they would have to show how Congress' ruling contravenes the Constitution, when the Constitution grants Congress the authority to regulate commerce and decide matters of national security.