No one would. If there is a ban it would be a ban on contact with the regular economy. It would be a ban on buying/selling dollars or goods/services with BTC. So you’d stop computing because if no one (or not enough people) can use the result of the computation there is no economic compensation for it.
To ban mining itself (calculation) you could only address things like construction permits or environmental permits for industrial mining operations. That’s also easy, and in no way interferes by saying what anyone “can compute”.