"The advice warns:
• Ripa does not allow mass interception of contents of communications between two people in the UK, even if messages are routed via a transatlantic cable.
• The interception of bulk metadata – such as phone numbers and email addresses – is a "disproportionate interference" with article 8 of the ECHR.
• The current framework for the retention, use and destruction of metadata is inadequate and likely to be unlawful.
• If the government knows it is transferring data that may be used for drone strikes against non-combatants in countries such as Yemen and Pakistan, that is probably unlawful.
• The power given to ministers to sanction GCHQ's interception of messages abroad "is very probably unlawful"."
http://www.theguardian.com/uk-news/2014/jan/28/gchq-mass-surveillance-spying-law-lawyer