1. A contract concluded between persons who, or whose agents, are in the same country at the time of its conclusion is formally valid if it satisfies the formal requirements of the law which governs it in substance under this Regulation or of the law of the country where it is concluded.

2. A contract concluded between persons who, or whose agents, are in different countries at the time of its conclusion is formally valid if it satisfies the formal requirements of the law which governs it in substance under this Regulation, or of the law of either of the countries where either of the parties or their agent is present at the time of conclusion, or of the law of the country where either of the parties had his habitual residence at that time.

3. A unilateral act intended to have legal effect relating to an existing or contemplated contract is formally valid if it satisfies the formal requirements of the law which governs or would govern the contract in substance under this Regulation, or of the law of the country where the act was done, or of the law of the country where the person by whom it was done had his habitual residence at that time.

4. Paragraphs 1, 2 and 3 of this Article shall not apply to contracts that fall within the scope of Article 6. The form of such contracts shall be governed by the law of the country where the consumer has his habitual residence.

5. Notwithstanding paragraphs 1 to 4, a contract the subject matter of which is a right in rem in immovable property or a tenancy of immovable property shall be subject to the requirements of form of the law of the country where the property is situated if by that law:

(a) those requirements are imposed irrespective of the country where the contract is concluded and irrespective of the law governing the contract; and

(b) those requirements cannot be derogated from by agreement.