As a general rule, no, the government is prohibited from paying the travel expenses of those attending meetings.  31 U.S.C. § 1345.  However, if an individual is providing a direct service to the Government, for example, speaking at the event, he may be put on invitational travel orders, pursuant to 5 U.S.C.§ 5703.
 

Appropriated funds may not be used to cover transportation expenses of meeting attendees, including local transportation.  31 U.S.C. § 1345.  However, if the contractor determines that the provision of transportation for conference attendees would be a personal convenience, the contractor may provide transportation and include the cost in the attendees’ personal convenience fee. 
 

Yes, speakers provide a direct service to the government so they may be put on invitational travel orders pursuant to 5 U.S.C. § 5703.  See also Honoraria.