The parties to the cross-border sale of goods can agree on the application of national law. If the parties do not choose national law, the European ROME I-Regulation applies to contracts within the European Union and other states that were entered into after December 17, 2009. Art. 4 (1) a) of the Regulation provides that the law of the state in which the seller has his usual place of business applies to the contract.
If two parties have their places of business in different states and both states have either ratified CISG or their rules of international private law lead to the application of the law of a State which has ratified the Convention, CISG will apply. All European countries, except the UK, Ireland, Portugal and Malta have ratified CISG. CISG applies in all 50 states of the U.S.A.
Parties can opt into the CISG or opt out of the CISG. If German law is chosen by the parties and an exclusion of CISG is desired, such exclusion must be specifically mentioned in the contract.
The sales transaction must concern the sale of goods. Sales to consumers are excluded. An oral contract for sale of goods is enforceable despite the absence of any writing. Some states (Russia, China, Argentina) have entered a reservation to exclude oral contracts. "General Terms and Conditions of Business" must be explicitly communicated in order to part of the transaction. The offeror of the terms has the burden of proof.