Yes, if you are a male.  The law says that all men living in the United States who are ages 18 through 25 (not yet 26) must register, except those who are in valid non-immigrant status (e.g., students, visitors, and people who have been permitted to come to the U.S. for limited periods of time, etc.).  The Selective Service interprets this to mean that undocumented men must register.  The time to register is within a 60 day period beginning 30 days before your 18th  birthday. [1]  Most eligible men do in fact register (about 99% of those ages 20 to 25) and if you don’t you are technically in violation of the law.  You do have choices; for advice, contact a military draft counselor, for example at the Quaker Meeting in D.C. or Sandy Spring, Md. or the Center for Conscience and War in D.C. (who will in most cases recommend you register). [2]  You can register when getting a driver’s license and also online at https://www4.sss.gov/regver/register1.asp.

[1] 50 App. U.S.C. § 453.

[2] Center for Conscience and War, 1830 Connecticut Ave. N.W., Washington, DC 20009, tel: 202-483-2220. Web site at http://www.centeronconscience.org .  Sandy Spring Friends Meeting, 17715 Meetinghouse Road, Sandy Spring, MD 20860, tel:  301-774-9792.  And DC Friends Meeting, 2111 Florida Ave., N.W., Washington, DC 20008, tel: 202-483-3310.