Verified answer

if you come back by land, you can come back with proof of citizenship and identification.

you might have them contact the nearest us embassy or consulate in mexico if you have further questions.

this website might help and the contacts within it might help too:

http://travel.state.gov/

all children since birth now need a passport (the law ) how did you smaller sister get out without a passport ? did they traveled by land ?

here is what the law says :

Travel by air

Since January 23rd, 2007, the U.S. Western Hemisphere Travel Initiative requires travelers entering or re-entering the United States by air to present a passport. So you'll need to show a passport if you're going back to the U.S. even if you don't need one to enter Mexico.

# Travel by land or sea #

Those traveling by land or sea will # not # be required to present a passport until 2008 (perhaps later), and there is a PASS card (Passport card) in the works that will be credit-card sized and cost less than a passport, which will allow travel in the United States, Canada, Mexico, the Caribbean and Bermuda.

A passport is the best form of ID

It's a good idea to get a passport if you're planning to travel to Mexico, whether or not it is an official requirement. A passport is the best form of international identification and having one may help you avoid hassles. See the links on the right for information on applying for a U.S. passport.

do relay theses informations to your mother before she comes back :-)

HJZ answered it best above. Though, if your sister ( American Citizen by birth ) and your Mother ( who is Landed Permanet Resident of the USA ) should not have difficulty getting back in to the USA IF. . . . .

they come back in via a Land Border Crossing.

If they come back via Air ( flying back in to the USA ) they defintely need a US Passport ( your sister ) and your Mom will require a Mexican Passport.

Side note : Message to Clark 6561 - making stupid comments about a person's ethnic background or the country they come from is really not called for !!! Grow up a be a true mature American and stop making " generalizations " based upon your ignorance. I am a Canadian ( by birth and lived there for 42 years ). I currently live in Pennsylvania and I am very happy to call the USA my new home since 2004.

Making comments like that are not called for - grow up.

Learn to listen to people from various countries and various ethnic backgrounds maybe you will be shocked at how much you will learn from these people and how wonderful people can be if you give them the opportunity to be themselves.

Stop " sterotyping " people. Think before you write down your comments. What you write comes from your heart.

Your sister: Yes she needs to obtain a US Passport.

Your mother: Since she is only a resident she will have to travel on her mexican passport but have her green card in hand to get back into the US. She can contact the nearest Mexican Consulate in the US to get her Mexican passport.

Everyone needs a passport now. They are going to have a hard time getting back.

you want a passport organic and easy. you are able to reapply and characteristic the application rushed. it is going to fee you, besides the undeniable fact that it may properly be accomplished. there is room to describe having lost the unique. do not attempt to flow without. you'll in reality land up going living house.

omg. there is a new rule that just went into place. the western hemishphere travel initiative. you now must have a us passport to get in and out of the us even if you are a us citizen. go to www.state.gov to learn more.

ps the new land travel rule may change and go into force asap. the us ambassador to canada just announced that to canada.

you only need passport when flying if they drove over the border you do not need a passport.

They are Mexicans again why dont you go join em they aint getting back in and if they do its gonna take a few years........Adios Amigo