The Congress has full authority to determine all laws dealing with Immigration into the United States. They can set any limits, establish any restrictions and create any law in regards who can and can not LEGALLY enter the Country. This INCLUDES making it illegal to enter the Country with out permission or following such laws as established by Congress.
Article 1 section 9
UNITED STATES CONSTITUTION
Section. 9.
The Migration or Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred and eight, but a Tax or duty may be imposed on such Importation, not exceeding ten dollars for each Person
Article 1 section 9
UNITED STATES CONSTITUTION