The same way you ban pirated media from being downloadable on the Internet: not effectively.

I'm old enough to remember "this shirt is a munition" and the DeCSS t-shirt.

Trade restrictions, sanctions. You can't effectively ban for individuals, but you can make it so legally risky for US based companies that it becomes effectively illegal as no US company will touch them, nor host them.

In the same way you can for any digital information?

How do you ban melted sand?