His "prescription" was to restrict the immigration of Southern and Eastern Europeans.  And his writings played a key role in the eventual passage of "National Origin" quota laws that did just that.

In the Emergency Quota Act of 1921 , Congress passed a new type of immigration law.  It limited the number of immigrants entering the United States in any one year to 3 percent of the size of each nationality group that had been living in the United States in 1910.  This policy favored the older Anglo-Saxon and northern European stock, who were more numerous than immigrants from southern and eastern Europe in that year.

The maximum annual quota was set at 357,802.  Of this total, approximately 56 percent was allotted to immigrants from northern and western Europe.  Eastern and southern European immigrants received a quota of about 44 percent.  The quota system drastically limited immigration from eastern and southern Europe, which had been running four times as large as that from the rest of Europe.

Many Americans were unhappy with the Immigration Act of 1921 because they felt that it still admitted too many of the "wrong" kinds of foreigners.  To some extent, this attitude was a product of the times.  The most extreme position was taken by the Ku Klux Klan.  The Klan was anti-black, anti-Catholic, anti-Jewish--against everybody not white, Anglo-Saxon, and Protestant.

The vast majority of Americans had little interest in the KKK.  Yet at the same time many felt some of the same feeling--concern about radical political ideas, the impact of Catholics and Jews on American society, and the "race degradation" of the American "stock" that supposedly was due to the influx of inferior Southern and Eastern Europeans.   Many believed that too many foreigners would upset the "racial" balance of America and that immigration had gone far enough.

As immigration again reached high levels after the lull during World War I, popular pressure for a more stringent policy increased.  Congress responded by passing a new and more drastic immigration law in 1924.  The Immigration Act of 1924 created a permanent quota system (that of 1921 was only temporary), reducing the 1921 annual quota from 358,000 to 164,000.  In addition, the Act reduced the immigration limit from 3 percent to 2 percent of each foreign-born group living in the United States in 1890.  Using 1890 rather than 1910 or 1920 excluded the new wave of foreign-born from southern and eastern Europe from quotas truly proportionate to their new numbers in the population. Finally, the act provided for a future reduction of the quota to 154,000.

The new law cut the quota for northern and western European countries by 29 percent, but slashed that for southern and eastern Europe by 87 percent. Italy's quota, for example, was reduced from 42,057 to 3,845 persons.