By presenting to the court a pleading, written motion, or other paper — whether by signing, filing, submitting, or later advocating it — an attorney or unrepresented party certifies that to the best of the person's knowledge, information, and belief, formed after an inquiry reasonable under the circumstances:
(1) it is not being presented for any improper purpose, such as to harass, cause unnecessary delay, or needlessly increase the cost of litigation;
(2) the claims, defenses, and other legal contentions are warranted by existing law or by a nonfrivolous argument for extending, modifying, or reversing existing law or for establishing new law;
(3) the factual contentions have evidentiary support or, if specifically so identified, will likely have evidentiary support after a reasonable opportunity for further investigation or discovery; and
(4) the denials of factual contentions are warranted on the evidence or, if specifically so identified, are reasonably based on belief or a lack of information.
Basically, an attorney is only supposed to file a law suit in good faith and on reasonable belief in the merits of the claim (bullshit slip and fall cases, anyone?). Anyway, here is the headnote:
Rule 11's admonition that every lawyer do necessary work to find law before filing brief applies even to lawyers who have two varsity letters in a collision sport and who were presidents of their fraternities. Chambers v. Am. Trans Air, Inc., 17 F.3d 998 (7th Cir. 1994)