What are the restrictions on loading WASM modules?

I get this error when trying to use an emscripten based WASM library:

Error: CompileError: WebAssembly.Module(): Wasm code generation disallowed by embedder

The docs show loading WASM like this:

import mod from './simple.wasm'

What are the supported methods of loading wasm data?

How does the CF runtime know if the WASM data comes from an import or a fetch('data:application/octet-stream;base64,...')?