The non-symbolic move is to designate them a foreign terrorist organization via the state department. Because very simply, it's unambiguously true, Antifa does operate as a decentralized transnational terror network, sometimes with organized groups/cells and other times as lone-wolf style attacks. The state department has designated decentralized transnational terror networks as FTOs before. This opens up an ability to prosecute under material support laws in a different way. Take for example this post from Corvallis Antifa, this isn't happening in a vacuum, it's enabled by another set of antifa in Italy who support hundreds of violent extremist groups across the world with their platform that shares arson guides, calls to violence, explosives, and other crime guides. You could point to other example of international groups like Antifa international or the sharing of terror content and tactics overseas like Autonomous German Antifa tactics being brought to America. There is recent precedent in the courts for this being done to accelerationist groups (done at the end of the Biden administration) that operate in a similar decentralized transnational way. US citizens who have operated in America have been charged with FTO material support cases for this. Antifa has committed more violence and most certainly more high-profile violence then those groups. Treat them the same way.