So, in mid-1949, Tsien executed the rite demanded of alliens who wish to remain indefinitely in this country: he went to Canada, acquired a permanent resident's visa and reentered with it.

In 1935 pre-examination was extended to illegal immigrants to facilitate their legalization. A formal agreement between the U.S. Department of State and Immigration Service and their Canadian counterparts detailed procedures whereby an immigrant in the U.S. without a visa could be "pre-examined" for legal admission, leave the country as a "voluntary departure," proceed to the nearest American consul in Canada, obtain a visa for permanent residence, and reenter the United States formally as a legal admission.

The INS thus suspended state territoriality in order to unmake the illegal status of certain immigrants. Although the whole procedure was a bureaucratic arrangement, the INS and State Department would not simply issue new documents granting an alien's legal status. The alien had to cooperate by physically leaving and reentering the country, to enact a voluntary departure and a legal admission. Some aliens failed to understand the necessity of the performance (or could not afford to make the trip to Canada) and wondered why, if it was willing to adjust their status, the INS would not simply leave them alone.