The employer should find out how to make this person legal, which will involve hiring an immigration lawyer to help in the process.
Thanks for you input. Unfortunately life often doesn't provide easy answers-- and dealing with "illegal" immigration is one of these times.
If you read some of the other threads I post to, you will know that I am involved in the immigrants rights movement. This is because I have been personally confronted with a very similar situation where someone close to my family is undocumented.
It is almost impossible for people who have lives here illegally to become legal. The very act of attempting to become legal puts one at risk of being deported. Lawyers (whose duty it is to advise their clients what is best for their interests) will tell "illegal" immigrants to do nothing (that is not to try to change their status).
This is is the core of the current political debate on immigration-- wether to provide a way for undocumented immigrants to become legal. The current law makes this very difficult.
I wasn't intending to discuss this specific issue in this thread... but I want to point out that the solution given in the housekeeper example is not a good one.
The housekeeper (if she understands her legal situation) will probably wisely refuse the help (especially after the lawyer explains the situation) and the moral dillemma-- whether to keep the housekeeper (in violation of the law), or to force her to put herself at risk of deportation is still there.
Of course in the other less current examples there are also no easy answers... hiding slaves, or resisting war. It is often the case where the stark options are breaking the law or holding to one's moral values.
Life doesn't always provide an easy way out.