According to the United States' 1907 Gentleman’s Agreement with Japan, the Japanese government would stop issuing passports to citizens intending to immigrate to the US.
the Japanese government would only issue 5,000 passports per year to citizens intending to immigrate to the US.
the US government could revoke the citizenship of Japanese immigrants already settled in the US.
the US government could refuse to grant passports to American citizens intending to immigrate to Japan.