Disclosure of keys. Under UK law you can be issued with a Section 49 by the authorities to decode and hand over any encrypted data as plain text. Two people recently have been charged for failing to decode their data, and it is unclear of what original charges they were arrested on.
There is an article at the Register regarding this.
Also here is some information from the government web-site .
It is an offence for a person who has been given a notice to knowingly fail to disclose the information required.