US federal law makes it crime for a person who has been removed (deported) to reenter the United States. 8 U.S.C. 1326 states as follows:
(a) In generalSubject to subsection (b), any alien who—
(1) has been denied admission, excluded, deported, or removed or has departed the United States while an order of exclusion, deportation, or removal is outstanding, and thereafter
(2) enters, attempts to enter, or is at any time found in, the United States, unless (A) prior to his reembarkation at a place outside the United States or his application for admission from foreign contiguous territory, the Attorney General has expressly consented to such alien’s reapplying for admission; or (B) with respect to an alien previously denied admission and removed, unless such alien shall establish that he was not required to obtain such advance consent under this chapter or any prior Act,
shall be fined under title 18, or imprisoned not more than 2 years, or both.
(b) Criminal penalties for reentry of certain removed aliensNotwithstanding subsection (a), in the case of any alien described in such subsection—
(1) whose removal was subsequent to a conviction for commission of three or more misdemeanors involving drugs, crimes against the person, or both, or a felony (other than an aggravated felony), such alien shall be fined under title 18, imprisoned not more than 10 years, or both;
(2) whose removal was subsequent to a conviction for commission of an aggravated felony, such alien shall be fined under such title, imprisoned not more than 20 years, or both;
(3) who has been excluded from the United States pursuant to section 1225(c) of this title because the alien was excludable under section 1182(a)(3)(B) of this title or who has been removed from the United States pursuant to the provisions of subchapter V, and who thereafter, without the permission of the Attorney General, enters the United States, or attempts to do so, shall be fined under title 18 and imprisoned for a period of 10 years, which sentence shall not run concurrently with any other sentence. or
(4) who was removed from the United States pursuant to section 1231(a)(4)(B) of this title who thereafter, without the permission of the Attorney General, enters, attempts to enter, or is at any time found in, the United States (unless the Attorney General has expressly consented to such alien’s reentry) shall be fined under title 18, imprisoned for not more than 10 years, or both.
For the purposes of this subsection, the term “removal” includes any agreement in which an alien stipulates to removal during (or not during) a criminal trial under either Federal or State law.
(c) Reentry of alien deported prior to completion of term of imprisonment
Any alien deported pursuant to section 1252(h)(2)  of this title who enters, attempts to enter, or is at any time found in, the United States (unless the Attorney General has expressly consented to such alien’s reentry) shall be incarcerated for the remainder of the sentence of imprisonment which was pending at the time of deportation without any reduction for parole or supervised release. Such alien shall be subject to such other penalties relating to the reentry of deported aliens as may be available under this section or any other provision of law.
As can be seen from that portion of the US Code, a person who has been denied admission, excluded, deported, or removed from the USA can be imprisoned for 2 years under federal law if they reenter the USA. However, the possible penalty increases to 10 years in prison if the person has been convicted of a non-aggravated felony or 3 misdemeanors of certain types. In the event that there is a conviction for an aggravated felony, then the maximum prison sentence is further increased to 20 years. There are also other convictions that can result in an increased sentence for a person who is federally charged with illegal reentry.
A person facing an illegal reentry charge is well advised to seek an attorney at once, as it is vital to properly handle the case.