"The Mann Act, is a United States law, passed June 25, 1910 (ch. 395, 36 Stat. 825; codified as amended at 18 U.S.C. §§ 2421–2424). It is named after Congressman James Robert Mann, and in its original form prohibited white slavery and the interstate transport of females for 'immoral purposes'. Its primary stated intent was to address prostitution, immorality, and human trafficking; however, its ambiguous immorality language allowed selective prosecutions for many years, and was used to criminalize forms of consensual sexual behavior. It was later amended by Congress in 1978, and again in 1986 to apply only to transport for the purpose of prostitution or illegal sexual acts."
The Mann Act applies to transporting any minor across state lines for the purpose of committing an illegal act. Another federal angle is the use of telephones to arrange meetings with minors for illegal acts. Federal crime.