If he and his camp followers are correct that borders should be no barrier, then disband the IRS and send your taxes to the UN.
Pretty much the first responsibility of a government is to protect the border. From the US constitution, defense is listed right after paying back public debt and before general public welfare in the first statement of duties of Congress:
"The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States. (Section 8)"