Very odd that he wouldn't accept the offer of an attorney, considering the seriousness of the charges and the amount of the bond. I'm sure he qualifies. I would like to see a transcript of the detention/bail hearing.
http://www4.law.cornell.edu/uscode/html/uscode18/usc_sec_18_00003142----000-.html
(3) Subject to rebuttal by the person,
it shall be presumed that no condition or combination of conditions will reasonably assure the appearance of the person as required and the safety of the community if the judicial officer finds that there is probable cause to believe that the person committed
(A) an offense for which a maximum term of imprisonment of ten years or more is prescribed in the Controlled Substances Act (21 U.S.C. 801 et seq.), the Controlled Substances Import and Export Act (21 U.S.C. 951 et seq.), or chapter 705 of title 46;
(B) an offense under section 924 (c), 956 (a), or 2332b of this title;
(C) an offense listed in section 2332b (g)(5)(B) of title 18, United States Code, for which a maximum term of imprisonment of 10 years or more is prescribed;
(D) an offense under chapter 77 of this title for which a maximum term of imprisonment of 20 years or more is prescribed; or
(E) an offense involving a minor victim under section 1201, 1591, 2241, 2242, 2244 (a)(1), 2245,
2251, 2251A,
2252 (a)(1), 2252 (a)(2), 2252 (a)(3),
2252A (a)(1), 2252A (a)(2), 2252A (a)(3), 2252A (a)(4), 2260, 2421, 2422, 2423, or 2425 of this title.
(i)
Contents of Detention Order. In a detention order issued under subsection (e) of this section, the judicial officer shall
(1) include written findings of fact and a written statement of the reasons for the detention;
(2) direct that the person be committed to the custody of the Attorney General for confinement in a corrections facility separate, to the extent practicable, from persons awaiting or serving sentences or being held in custody pending appeal;
(3) direct that the person be afforded reasonable opportunity for private consultation with counsel; and
(4) direct that, on order of a court of the United States or on request of an attorney for the Government, the person in charge of the corrections facility in which the person is confined deliver the person to a United States marshal for the purpose of an appearance in connection with a court proceeding.
It would seem that the charges against him fall under some of those listed in 3E above (underlined and linked), and the way it reads to me he can (and should) be held without bail. Again, he was taken into custody by Federal agents, and what he's accused of clearly fall under Federal statutes, yet it's not clear to me that he'll be tried in Federal or state court.