system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If copyright protection ever actually runs out for Mickey Mouse, how could he be used by non-Disney parties without violating trademark law?
gpt
Copyright and trademark are two different things.

If Disney ever fails to have their politicians extend the copyright and Steamboat Willy falls into the public domain, it won't mean that you can freely violate Disney's trademarks.

You will be able to copy, view and show the animated film without paying Disney and even make derivative works of it.

Something similar to what would happen to Mickey Mouse is probably the current status of Tarzan. The first few novels featuring Tarzan are out of copyright and you can freely download copies of them, but the authors estates claims a trademark on Tarzan.

People who have tried to use the public domain status of Tarzan to make derivative works like comics featuring the character have been sued by the estate for violating the trademark.

So if Steamboat Willie ever became public domain Disney's lawyers would probably sue the pants of anyone attempting to create their own works featuring Mickey Mouse.