Opinions given by Advocate's General are highly influential and are usually followed by the Court.
The slogan, "Have a break... Have a Kit-Kat" and the name "Kit-Kat" have been registered trade marks for many years.
The chocolate bar itself dates back to 1935, while the name Kit-Kat was adopted two years later, in memory of an 18th Century Whig literary club called the Kit Kat club.
In 1976 the then brand owner tried to register the phrase "Have a break" as a trade mark, but was refused. This attempt was followed 19 years later by the current owner, Swiss food giant Nestlé, which applied to register the mark in March 1995.
The application was opposed by rival Mars UK Ltd, on the grounds that it did not comply with rules for registration laid out in the Trade Mark Act 1994. The Hearing Officer agreed, on the basis that the mark was "devoid of any distinctive character".
Nestlé eventually went to the Court of Appeal, which had to consider firstly whether the phrase on its own was devoid of distinctive character, and secondly, if it was, whether it had acquired a distinctive character before the application for a trade mark was made, through association with "Have a Kit-Kat".
The Court ruled that that there was no distinctive character in the phrase "Have a break", but, for technical reasons to do with interpreting the Trade Mark Act in accordance with Community Law, the Court decided that the second question – whether distinctiveness had been acquired – had to be referred to the European Court for clarification.
It is this referral that has now been considered by Advocate General Kokott.
According to Kokott, principal trade marks with a strong distinctive character can transfer distinctive character to elements of the mark, but this distinctiveness will not be of the same nature as that possessed by the principal mark.
"The use of a word sequence as part of a word mark can, as a matter of principle, lead to that word sequence acquiring the requisite distinctive character in order to be registrable as a trade mark," wrote Kokott in her Opinion.
"In order to prove that distinctive character has been acquired through use as an element of a composite mark the relevant consumer groups must be shown to understand that the element in question, if used separately, designates a product as originating from a specific undertaking, thus distinguishing it from products of other undertakings," she concluded.
In essence this means that even if consumers automatically complete the slogan "Have a break" with "Have a Kit Kat", this is not sufficient to prove distinctive character. Proof would only be provided by showing that consumers would attribute a product containing the mark "Have a Break" to the maker of Kit Kats – Nestlé.