Your ultralight and Cessna 152 aren't typically allowed within 10 nm of the
president's aircraft, for presumably security reasons, but this is allowed:

"Man carrying assault weapon attends Obama protest"
http://news.yahoo.com/s/ap/20090817/...rotesters_guns

(I wish the AOPA, EAA, and the rest of the alphabet soup of private
aviation organizations had the political clout the NRA had. My guess is it
comes down to being free with the donations and having a single narrow
focus. The aviation groups have no political focus.)

VIP TFRs never made a lot of security sense (to me, anyway.)