If you have lived undocumented in the United States and then willfully left the country, you may find that you are barred from entering the county gain for a certain period of time. If this happens, the only hope for you will be a waver.
There is a number of ways in which you can accumulate unlawful presence. One is by entering the United States without inspection, which could commonly called “crossing the border.” Another way would be by overstaying your visa. Finally your sojourn in the United States could be ruled unlawful presence if by violating your current status if you have been notified by the government that you have done so. NOTE: Anyone who commits fraud or who otherwise misrepresents himself will be banned permanently from entering the United States.
The amount of time for which you will be banned will be determined by the length of your unlawful presence. For example, if you have accumulated 180 days of unlawful you will not be permitted to return to the United States for 3 years. If you stayed one year or more unlawfully, you will not be permitted to return for 10 years. Both bans start from the day the law took effect, which was April 1, 1997.
To be allowed to enter again you would need a waiver, which might be granted if one of your resident relatives has an illness or who would otherwise suffer “extreme hardsship” should your waiver not be approved. Keep in mind that both “unlawful presence” and “extreme hardship” are difficult to determine, and you will definitely need an experienced attorney on your side to guide you through the process.