Commentaries: Art. 1087

The form of a declaration on a bill of exchange is determined according to the law of the country in whose territory the declaration was signed.
However, where a declaration on a bill of exchange that is invalid under the previous paragraph would be valid under the law of the country in whose territory a subsequent declaration is signed, the validity of the later declaration is not affected by any formal defects of the earlier declaration.
Similarly, a declaration on a bill of exchange given by one Swiss national abroad is valid in relation to another Swiss national in Switzerland provided it satisfies the formal requirements laid down by Swiss law.