Rabbeinu Baruch (the author of the Sefer Hateruma, cited in Teshuvot Harosh 2:1) argues that Chadash outside of Israel is forbidden only rabbinically. He further agrees that the rabbinical decree to observe Chadash outside of Israel applies only in those lands that are close to Israel, such as Egypt. He notes that when Chazal instituted that Terumot and Maaserot be separated in Chutz La'aretz, they imposed this rule only in the lands that are close to Israel (see Rambam Hilchot Terumot 1:1).
The Magen Avraham (489:17) and the Aruch Hashulchan (Yoreh Deah 293:20-21) conclude that this is the most convincing defense of the practice to be lenient regarding Chadash. Nonetheless, the Magen Avraham counsels that a scrupulous individual should try to avoid relying on this very lenient approach. Furthermore, the Vilna Gaon (Biur Hagra Yoreh Deah 293:2) vigorously rejects this leniency.
