Art. 94 CISG
(1) Two or more Contracting States which have the same or closely related legal rules on matters governed by this Convention may at any time declare that the Convention is not to apply to contracts of sale or to their formation where the parties have their places of business in those States. Such declarations may be made jointly or by reciprocal unilateral declarations.
(2) A Contracting State which has the same or closely related legal rules on matters governed by this Convention as one or more non-Contracting States may at any time declare that the Convention is not to apply to contracts of sale or to their formation where the parties have their places of business in those States.
(3) If a State which is the object of a declaration under the preceding paragraph subsequently becomes a Contracting State, the declaration made will, as from the date on which the Convention enters into force in respect of the new Contracting State, have the effect of a declaration made under paragraph (1), provided that the new Contracting State joins in such declaration or makes a reciprocal unilateral declaration.
Contracting States that have made an Art. 94 CISG reservation:
Overview of case law on Art. 94 CISG: UNCITRAL Digest
The UNCITRAL Digest on the CISG can be used as a starting point to discover the relevant case law on this article.