Flast exception:  logical nexus between taxpayer & claim.
i.   there must be a logical link between the status he asserts and
the type of legislative appropriation  involved
(it must always be a GW 1.8 appropriation by congress)
ii.  a logical link (or nexus) between the status he asserted and
the precise nature of the C’al right asserted
(can be a general rule about the C that congress is violating, but
one that you have a vested right/interest in; you must have a
personal/property interest at stake)
-    establishment clause is
-    5th am. d.p. is not