The first step these so called "undocumeted migrants" do is break the law by coming here. After that all laws are subject to voluntary compliance. See here in California, it's only those who have something to lose that must comply.
Case in point: A very good friend of mine is a painting contractor, licensed, insured, bonded, carries the required workman's commpensation insurance, and requires all of his hispanic workers to file and document appropriate I-99 forms, etc. His business has been in steady decline the past several years because hispanics who carry none of the required, licenses, insurances, or document their employees can underbid him on every job. He has been forced to deal in the highly competitive commercial painting sector, where being licensed, insured, etc. is required and audited. Unfortunately the bidding process is long and sometimes corrupt. Meanwhile his children have to compete for classroom space in schools supported by the property taxes he pays with the children of the so called "undocumented migrants."