Using the JAXB SchemaFactory I thought it was pretty easy to work around loading schemas from the net and using the ones included in our .jars instead. But somehow that didn't work out, the base schemas were still loaded through the internet.
Smart people found out that the order of the schema URLs when giving them to the SchemaFactory plays a role, and it turns out to be true! I've just opened a pull request that fixes the problem in deegree.
For it to work the schemas need to be in reverse order of inclusion, so put the schema without dependencies first and so on.