官方文件是這麽說的：

If you are in the United States and wish to travel abroad, you do not need to aaply for advance parole if both conditions described below are met:

1. You are an H-1, temporary worker, or H-4, spouse or child of an H-1.

2. A form I-485, Application to Register Permanent Residence or Adjust Status, was filed on your behalf and is pending with the USCIS.

However, upon returning to the United States, you must present your valid H nonimmigrant visa and continue to remain eligible for that status.

對加拿大公民來說，關鍵是H nonimmigrant visa。但是加拿大公民又不需要visa，如果你去使館，我甚至懷疑給不給你簽visa，這似乎是一個灰色區域。