There is a guide line. Have a look..


ICO guidance

Updated in May 2012, our cookies guidance (pdf) sets out the changes to the cookies law and explains the steps you need to take to ensure you comply. The updated guidance provides additional information around the issue of implied consent:

    Implied consent is a valid form of consent and can be used in the context of compliance with the revised rules on cookies.
    If you are relying on implied consent you need to be satisfied that your users understand that their actions will result in cookies being set. Without this understanding you do not have their informed consent.
    You should not rely on the fact that users might have read a privacy policy that is perhaps hard to find or difficult to understand.
    In some circumstances, for example where you are collecting sensitive personal data such as health information, you might feel that explicit consent is more appropriate.


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Hello,

Where the use of the cookie type device does involve the processing of the personal data, service providers will need to make sure they comply with additional requirements of the data protection.