Some chemistry journals do not allow you to publish if you place a copy on a preprint server like arxiv. The key to this battle will be funding agencies.
Well... you could still make the copy available after the article was published.
If you don't mind breaking your contract with the publisher.
What can they do against it?
Sue you for damages.
You mean, all $0 of them?
You mention chemistry. I don't know anything about chemistry journals, but given the precedent set by other fields, I feel that chemists don't have a good excuse for locking their research up behind paywalls.