In order to qualify an individual as an L-1 nonimmigrant, the employer must filed Form I-129, Petition for a Nonimmigrant Worker, with the USCIS Service Center that has jurisdiction over where the work will be performed in the United States, with the appropriate supplement and supporting documentation. Once approved, if the prospective L-1 nonimmigrant is already in the United States, then his nonimmigrant status will be changed to the appropriate L-1 classification; if the individual is outside the United States, the appropriate U.S. embassy or consulate will be notified by USCIS of the approved L-1 petition and that individual may then go to that U.S. embassy or consulate to apply for an L-1 nonimmigrant visa.
The USCIS must approve a blanket petition. The petition may be approved initially for three (3) years. After the initial three (3) year period, the employer may apply for an extension of its blanket approval. If blanket approval is received, then a prospective L-1 nonimmigrant outside the United States may complete Form I-129S, Nonimmigrant Petition Based on Blanket L Petition, attaching Form I-171C which demonstrates the “blanket approval,” to the U.S. embassy or consulate having jurisdiction over their residence (unless they are visa exempt) or, if that individual is inside the United States in another nonimmigrant status, his employer should file the petition with the USCIS Service Center that approved the blanket petition.
Note that blanket petition procedures may not be used for specialized knowledge positions unless they are “professional” in nature.