Definitions of exigent on the Web:

EK-suh-juhnt\, adjective: 1. Requiring immediate aid or action; pressing; critical. 2. Requiring much effort or expense; demanding; exacting.
www.kwintessential.co.uk/crossculturalnews/archives/cat_expandyourvocabulary.html

clamant: demanding attention; "clamant needs"; "a crying need"; "regarded literary questions as exigent and momentous"- H.L.Mencken; "insistent hunger"; "an instant need"
requiring precise accuracy; "an exacting job"; "became more exigent over his pronunciation"
wordnet.princeton.edu/perl/webwn

"White House spokesman Tony Snow said that's nothing new. “All this is saying is that there are provisions at law for — in exigent circumstances — for such inspections. It has been thus. This is not a change in law, this is not new.”