There is a commonplace within the European Community that any citizen has the right to stand for office. It is codified in the (foundering?) EU Charter as such, however no explicit mention is made of the right/freedom to speak one’s own language there…
That’s to be found in Rule 138 of the European Parliament’s Rules of Procedure, regarding General Rules for the Conduct of Sittings:
Rule 138 : Languages
1. All documents of Parliament shall be drawn up in the official languages.
2. All Members shall have the right to speak in Parliament in the official language of their choice. Speeches delivered in one of the official languages shall be simultaneously interpreted into the other official languages and into any other language the Bureau may consider necessary.
3. Interpretation shall be provided in committee and delegation meetings from and into the official languages used and requested by the members and substitutes of that committee or delegation.
4. At committee and delegation meetings away from the usual places of work interpretation shall be provided from and into the languages of those members who have confirmed that they will attend the meeting. These arrangements may exceptionally be made more flexible where the members of the committee or delegation so agree. In the event of disagreement, the Bureau shall decide.
Where it has been established after the result of a vote has been announced that there are discrepancies between different language versions, the President shall decide whether the result announced is valid pursuant to Rule 164(5). If he declares the result valid, he shall decide which version is to be regarded as having been adopted. However, the original version cannot be taken as the official text as a general rule, since a situation may arise in which all the other languages differ from the original text.”