These are the relevent documents for evaluating Block's 10 year ban:
the WADA code, starting page 72 describes a ban as a period of ineligibility.
"10.10.1 Prohibition Against Participation
During Ineligibility
No Athlete or other Person who has been
declared Ineligible may, during the period of
Ineligibility, participate in any capacity in a
Competition or activity (other than authorized
anti-doping education or rehabilitation programs)
authorized or organized by any Signatory,
Signatory's member organization, or a club or
other member organization of a Signatory’s
member organization, or in Competitions
authorized or organized by any professional
league or any international- or national-level
Event organization." Theres more, but thats a good preview.
Further, the ruling from Block's case (http://www.usada.org/uploads/ArbitrationAwardBlock.pdf) says:
"10.2.1 The "appropriate Consequences" imposed by the Panel is a ten year period of ineligibility commencing January 1, 2009 and ending on January 1 2019. Furthermore, all benefits, awards, titles, or remuneration from his involvement in track and field that flowed to Mr. Block as an Athlete Representative, from the period of January 1, 2009 to the date of this ruling shall be deemed forfeited and returned.
10.2.2 During his period of ineligibility, in addition to all other penalties or restrictions flowing from his ineligibility, Mr. Block is prohibited from participating in and having access to the training facilities of the USOC Training Centers, or other programs and activities of the USOC, including but not limited to, grants, awards, or employment pursuant to the USOC policies"
Sounds like he may be in violation of 10.2.2, depending on how you define the Olympic trials and USOC relationship. Otherwise, his "participation" in the event is debatable.
Still, can be considered shady and a conflict of interests, even if it does not violate the code