Unfortunately what we're seeing here is how student government office holders are typically official powerless figureheads meant to keep a lid on direct student action and unrest.
The MSU Bulk E-Mail policy allows for emailing "information regarding changes of University policies or procedures" but the privilege of exercising these speech rights is reserved to "only by University offices". Student governments are typically not an official university office and have no rights under any of the policies which exempt the first year teaching assistant.
Even worse, students are officially customers of the university yet constrained by draconian state laws which constrain their behavior as if they were minors in the care of the state and every university staff or faculty member were their guardians.
I encourage students everywhere to encourage their universities to adopt a "grown-up" student government policy where student office holders are official employees of the state and actually represent the interests of their constituents / the university's customers. Vote with your (or your parent's) dollars: attend schools which respect their customer's rights!