The EB-1C immigrant visa is specifically for managers or executives who qualify under the L-1A non-immigrant visa standards and wish to become permanent residents. Having been approved for an L-1A visa is not required to apply for an EB-1C but it will make for a stronger case if the applicant has an approved L-1A visa.
One requirement for this visa states that applicants must have been employed for one year of the last three years with a parent, affiliate, subsidiary, or branch of the U.S. petitioning company. Another important requirement is that the applicant will continue to provide their services to the same employer in a managerial or executive capacity. There are many other specific requirements for this immigrant visa which should be discussed with an experienced immigration attorney.
The EB-1C also has many benefits, one of which is that a PERM/labor certification is not required so the process to apply for a green card is much less complex than through other immigrant visa categories. Another important benefit to consider is that the family of the applicant, specifically the spouse and unmarried children under 21, may also be included in the application and receive green cards a well.
Once an EB-1C is approved there are two options on how to move forward. If the applicant is in the U.S. they can apply for adjustment of status or if they are outside the U.S. they may choose to process the case through consular processing in their home country. Whether to move forward with one process over another should be discussed with an immigration attorney as they will be able to provide you with the most beneficial course of action.