1.) Most countries have national laws but their enforcement differs. Priorities or for political reasons?

2.) In the US, the C.O.P.A. statute, restricting access to sexually explicit material was struck down as unconstitutional for reason of it's adult verification restrictions being technically unachievable. There is no AVS (adult verification system) that is sure to be accurate. The Parliament in the UK has taken a different approach ? the opt-in to porn one. Good luck if you expect John Q. Public to state that he wants authorization to view porn online ? that is ludicrous!! Hopefully, this UK law will meet it's death in the UK Courts.

More directly, DMCA is a US law ? it is only enforceable in the United States. Most countries are signatories to the Berne Convention of Copyright, making copyright internationally recognized.

Chinese persons need follow Chinese law, US persons need follow US Federal and State laws, EU persons need follow both EU statutes and their country's laws, etc. ... There is also certain limited International Law that the courts in some political jurisdictions will consider admissible and follow, limited being the key word.

There is no recognized world government that decrees the "Law of the Internet."