Subject matter jurisdiction is the sine qua non of the exercise of power by a federal court. One purpose of Rule 11 of the Federal Rules of Civil Procedure is to prevent an attorney from haling a party into federal court without having performed, at the very least, a reasonable inquiry into the jurisdictional underpinning of the lawsuit.
The facts necessary for our decision are undisputed. In May 1987, International Shipping Company, S.A. (“International”), a Panamanian company, through its agent Lygren Maritime Services, S.A. (“Lygren”); a Swiss corporation, allegedly entered into an agreement with Hydra Offshore, Inc. (“Hydra”), a corporation organized under the laws of Liberia, to buy a vessel called Friendship. After International had paid 10% on the total purchase price of $2,650,-000.00, Hydra sold the ship to Maryland Navigation Co. (“Maryland”), another Liberian corporation with New York as its principal place of business.
On June 1, 1987, upon International’s motion, the English High Court of Justice, Queens Bench Division, restrained Hydra from disposing of or moving the ship, pending the outcome of an arbitration in Britain. Shortly thereafter, appellants brought this action in the Southern District of New York. They alleged Hydra breached a contract to sell the Friendship to International and that Maryland, American General Resources, Astron Management Corp. (“As-tron”), James and Peter T. Pappas, and Richard Jaross,1 intentionally and tortiously interfered with its contractual relations with Hydra for the sale of the Friendship. The complaint asserted federal jurisdiction grounded on admiralty (28 U.S.C. § 1333), diversity of citizenship (28 U.S.C. § 1332), and the Convention on Recognition and Enforcement of Foreign Arbitral Awards (9 U.S.C. §§ 201-208).
On June 11, 1987, because of the British court’s order, appellants sought an order for a preliminary injunction to prevent Maryland or Hydra from selling, moving, chartering, or otherwise disposing of the vessel. Judge Leisure denied International’s request for a temporary restraining order by deleting language in the draft order which would have prevented appel-lees from selling or transferring the vessel pending the hearing scheduled for June 16. A copy of the order served on Friday, June *39012, 1987, by appellants’ attorney, however, did not reflect the deletion of the paragraph imposing a temporary restraining order, nor did the copy bear Judge Leisure’s signature.2
The jurisdictional grounds for issuance of the injunction were attacked for various reasons by Maryland Navigation in an affidavit filed with the court June 16, 1987. On June 30, Judge Leisure heard oral argument to determine whether subject matter jurisdiction existed. Finding no basis for jurisdiction, he dismissed the action. Ap-pellees then sought to impose Rule 11 sanctions against all appellants. The court ultimately imposed a $10,000 penalty on appellants’ counsel Golub, because “[wjhile seeking the drastic and extraordinary relief of a preliminary injunction ... [he] had clearly not examined the very basis for his presence in [the federal] Court.” International Shipping Co. v. Hydra Offshore, Inc., 675 F.Supp. 146, 154 (S.D.N.Y.1987).
The district court granted counsel’s motion for reargument of its decision, and some 11 months after the issuance of the original order heard reargument on both the amount and imposition of sanctions. Judge Leisure declined to amend his order, noting that no new arguments or evidence had been presented. Thereafter, counsel Richard Golub reinstated his appeal, which he had withdrawn pending the outcome of reargument.3
Rule 114 mandates sanctions where it is clear that: (1) a reasonable inquiry into the basis for a pleading has not been made; (2) under existing precedents there is no chance of success; and (3) no reasonable argument has been advanced to extend, modify or reverse the law as it stands. Cf. Norris v. Grosvenor Marketing Ltd., 803 F.2d 1281, 1288 (2d Cir.1986). The Rule “explicitly and unambiguously imposes an affirmative duty on each attorney to conduct a reasonable inquiry into the viability of a pleading before it is signed.” Eastway Construction Corp. v. City of New York, 762 F.2d 243, 253 (2d Cir.1986). This requirement assures that lawyers are prepared to demonstrate that they have done the necessary investigation prior to appearing in court. Golub’s arguments are examples of “post hoc sleight of hand” calculated to make plausible very tenuous jurisdictional claims. See Schwarzer, Rule 11 Revisited, 101 Harv.L.Rev. 1013, 1022 (1988).
Unfortunately, our dissenting brother misconstrues the reason sanctions were imposed in this case. In so doing he ignores the purpose for the revision of Rule 11. Its principal objective was to “reduce the reluctance of courts to impose sanctions by emphasizing the responsibilities of the attorney and reenforcing those obligations by the imposition of sanctions.” Fed.R.Civ.P. 11 Advisory Committee Note. The Rule compels us to focus on counsel’s conduct at the time of the submission in deciding if a reasonable inquiry has been made. Id.
The district court concluded that Rule 11 was violated because appellant failed to perform a reasonable inquiry into the applicable law prior to signing the complaint. Regardless of the validity of any argument Golub can now conjure to justify overlooking a well-established principle of *391law, he was required to conform with the law or be prepared to challenge it at the time he signed the complaint. Contrary to our dissenting brother’s view, we believe that the filing of a complaint in which Golub identified alien corporations on both sides of the litigation revealed that he was unaware of the complete diversity requirement. This fact is plainly revealed by the complaint itself, the colloquy before the court, and Golub’s contention that he should not be punished because he did not receive the opposition’s papers raising jurisdictional objections until the day before oral argument.
As we stated, appellants’ complaint alleged federal jurisdiction founded upon diversity, admiralty, and the Convention on the Recognition and Enforcement of Foreign Arbitral Awards. The admiralty and Foreign Arbitral Awards grounds, however, were both found to be jurisdictionally deficient. Golub does not contest those findings on appeal.5
Golub’s principal claim on appeal rests upon the premise that jurisdiction existed because Maryland Navigation Company’s principal place of business was New York, rendering it solely a citizen of that state for purposes of diversity under § 1332(c).6 As support for this proposition, Golub cites dicta in Bergen Shipping Co. v. Japan Marine Services Ltd., 386 F.Supp. 430 (S.D.N.Y.1974).
The general rule requiring complete diversity between opposing parties is explicit and unequivocal. As Judge Leisure properly concluded, “[a] cursory review of a hornbook or digest would have revealed [the] jurisdictional defect to [appellants’] counsel.” International Shipping, 675 F.Supp. at 152. See 1 Moore’s Federal Practice 110.75 (2d ed. 1986); 13B C. Wright, A. Miller, E. Cooper, Federal Practice and Procedure § 3604 (2d ed. 1984). Clearly, this rule applies in cases where aliens appear on both sides of a case. Corporacion Venezolana de Fomento v. Vintero Sales Corp., 629 F.2d 786, 790 (2d Cir.1980) (“[T]he presence of aliens on two sides of a case destroys diversity jurisdiction.”), cert. denied, 449 U.S. 1080, 101 5.Ct. 863, 66 L.Ed.2d 804 (1981). Accord ITT v. Vencap Ltd., 519 F.2d 1001, 1015 (2d Cir.1975). See also Hercules Inc. v. Dynamic Export Corp., 71 F.R.D. 101 (S.D.N.Y.1976).
In Venezolana, this court dealt with the applicability of 28 U.S.C. § 1332(c) to alien corporations. We decided that even if a corporation organized under the laws of a foreign nation maintains its principal place of business in a State, and is considered a citizen of that State, diversity in nonetheless defeated if another alien party is present on the other side of the litigation. Venezolana, 629 F.2d at 790. We postulated a situation in which such corporations would have “dual citizenship” — being regarded as citizens of both the State of their principal place of business and the nation under whose law it had been incorporated. Id. To the extent that the dicta in Bergen suggested that under § 1332(c) a corporation might be considered solely a citizen of the State of its principal place of business, *392its force was vitiated by our subsequent decision in Venezolana.7
In view of these precedents we are forced to conclude that a reasonable inquiry into the current law would have precluded the argument counsel made at the hearing on June 30 — that “[w]hether or not you have aliens on both sides [of a litigation is] irrelevant once their principal places of business are here in New York.” Nor could he have stated, after opposing counsel’s extended discussion of the controlling cases, “I don’t know what the reference is to dual citizenship.” Under current Second Circuit doctrine it would have been apparent — after a reasonable examination of the law — that Golub had no chance of succeeding based upon Bergen.8
In addition, we search in vain for any principled argument advanced by counsel to reverse or modify our holding in Venezo-lana. Instead, he insists that what was decided in that case was not, in fact, decided at all. Yet in Venezolana we concluded beyond cavil that, in this circuit, a corporation organized under the laws of a foreign nation remains an alien corporation under § 1332, even if its principal place of business is in one of the States. 629 F.2d 786, 790. We made this conclusion unmistakable by citing with approval Hercules, Inc. v. Dynamic Export Corp., 71 F.R.D. 101 (S.D.N.Y.1976), a case that criticized and rejected the Bergen analysis.
Appellants also claim that Judge Leisure erred in failing to hold an evidentiary hearing to determine the amount of sanctions — on the supposition that sanctions were imposed to compensate appellees. This argument fails for at least two reasons. At the outset it should be stated that appellants were permitted to reargue the Rule 11 motion, but failed to present any new evidence to attack the imposition or amount of sanctions. Moreover, we have previously rejected the notion that the imposition of sanctions pursuant to Rule 11 requires an evidentiary hearing. Oliveri v. Thompson, 803 F.2d 1265, 1280 (2d Cir.1986), cert. denied sub nom., County of Suffolk v. Graseck, 480 U.S. 918, 107 S.Ct. 1373, 94 L.Ed.2d 689 (1987); see also Fed. R.Civ.P. 11 Advisory Committee Note (“[T]he court must to the extent possible limit the scope of sanction proceedings to the record.”).
In any event, sanctions were imposed by the court below primarily to reprove appellants’ attorney rather than to compensate the opposing side for its expenditures in resisting the action. See International Shipping, 675 F.Supp. at 154-55. It is well settled that Rule 11 empowers judges with discretion to award that portion of a defendant’s attorney’s fee thought reasonable to serve the sanctioning purpose of the Rule. See, e.g., Eastway Construction Corp. v. City of New York, 821 F.2d 121, 123 (2d Cir.1987) (“Eastway II”). The scope of that discretion is broad. See, e.g., Calloway v. Marvel Entertainment Group, 854 F.2d 1452, 1476 (2d Cir.1988), cert. granted sub nom. Pavelic & Leflore v. Marvel Entertainment Group, — U.S. -, 109 S.Ct. 1116, 103 L.Ed.2d 179 (1989). And, an appellate court will apply an abuse of discretion standard upon review. Id. As we noted in Eastway II, “[t]he concept of discretion implies that a decision is lawful at any point within the outer limits of the range of choices appropriate to the issue at hand_” 821 F.2d at 123.
The district court had before it evidence that appellees expended $48,031.33 in the period between June 12 and June 30, 1987, opposing appellants’ motion for injunctive relief. Finding that a considerable amount of the work performed by appel-*393lees could be used in related court actions, the court declined to impose as sanctions the full amount of the costs incurred. Instead, Judge Leisure, after considering the nature of the violation of Rule 11 and the context in which it arose, with some reticence, imposed sanctions against counsel in the sum of $10,000. We cannot conclude that this amount exceeds “the outer limits of the range of choices appropriate to the issue....” Accordingly, Judge Leisure did not abuse his discretion in fashioning the sanction.
Appellants’ final argument is that the district court should have dropped Maryland Navigation from the litigation and retained jurisdiction over the case. But Judge Leisure, during the June 30 hearing on the preliminary injunction application, specifically asked Golub whether he would be willing to strike Maryland as a defendant in the action to preserve diversity. Golub refused, arguing: “If we drop Maryland — the title to the ship is now in Maryland’s name — I don’t know how we could get any relief against [them].” Research reveals no precedent that indicates that it is error for the court to fail to dismiss a party from an action so as to preserve diversity despite the plaintiff’s own choice to retain that party and in the absence of any motion to have that party removed.
Whether sanctions under Rule 11 may be imposed for an attorney’s failure to conduct a proper pre-trial inquiry into the court’s subject matter jurisdiction is a question that is quite distinct from the decision to impose sanctions for a frivolous appeal under Rule 38 Fed.R.Civ.P. We do not believe that Rule 38 sanctions are warranted here.
The quality of Justice depends upon our ability, to control the flood of litigation. Rule 11 requires that members of the bar avoid haphazard, superficial research. That requirement places the responsibility for properly invoking the power of the court on counsel as officers of the court. On these facts, that standard simply has not been met. Accordingly, we affirm.
. American General Resources Inc., is a domestic corporation organized under the laws of Connecticut. Richard Jaross is a resident of Connecticut and is the principal shareholder of American General. Astron is a domestic corporation with its principal place of business in New York. James Pappas, a resident of Massachusetts, is a principal shareholder in Astron and is also interested in Maryland Co. Peter Pappas resides in Connecticut and is a principal shareholder of Astron and is also interested in Maryland.
. The effect of the service of this purported copy of Judge Leisure's Order was to force counsel for appellees to labor over the weekend under the impression that the temporary restraining order was already in force. Whether innocent or otherwise, the service of an unconformed copy of an Order to Show Cause on extremely short notice, which incorrectly asserted the imposition of a temporary restraining order is a cause of concern.
. While International and Lygren also appeal the decision imposing sanctions, we read their participation as based upon the claim that the court erred in dismissing the suit for lack of subject matter jurisdiction. The appeal was concerned principally with the sanctions imposed on counsel.
.In pertinent part, Fed.R.Civ.P. 11 states: The signature of an attorney or party constitutes a certificate by the signer that the signer has read the pleading, motion, or other paper; that to the best of the signer’s knowledge, information, and belief formed after reasonable inquiry it is well grounded in fact and is warranted by existing law or a good faith argument for the extension, modification, or reversal of existing law, and that it is not interposed for any improper purpose, such as to harass or to cause unnecessary delay or needless increase in the cost of litigation.
. While appellants may have abandoned arguments for the court’s subject matter jurisdiction based upon admiralty and the Convention, we can and do take note that these claims were defective at the time the pleadings were signed, a fact that would have been apparent after a reasonable inquiry.
Judge Leisure correctly ruled that admiralty jurisdiction under 28 U.S.C. § 1333, does not exist in actions involving the breach of a contract for the sale of a vessel. See CTI-Container Leasing Corp. v. Oceanic Operations Corp., 682 F.2d 377, 380 n. 4 (2d Cir.1982); The Ada, 250 F. 194, 197-98 (2d Cir.1918) (Rogers, /., concurring).
Appellants’ contentions that jurisdiction could be premised on the Convention on the Recognition and Enforcement of Foreign Arbitral Awards, 9 U.S.C. §§ 201-208 were also appropriately rejected. The district court found the Convention inapplicable in this case because the party invoking its provisions did not seek either to compel arbitration or to enforce an arbitral award. See International Shipping Co. v. Hydra Offshore, 675 F.Supp. 146, 150-153.
. Appellants agreed at the June 30, 1987 hearing to drop Hydra in order to preserve diversity under § 1332. This, however, still left International and Lygren — both foreign corporations— on one side of the litigation and Maryland, a Liberian corporation on the other.
. In Bergen, the court premised its exercise of power on the existence of admiralty jurisdiction, rather than on the existence of diversity under its analysis of § 1332(c). Bergen Shipping Co. v. Japan Marine Services Ltd., 386 F.Supp. at 434.
. Judge Pratt’s reliance upon Chok v. S & W Berisford, PLC, 624 F.Supp. 440 (S.D.N.Y.1985) is misplaced. In Chok, defendants moved for imposition of sanctions alleging that the action "could only have been brought for ‘an improper purpose such as to harass or to coerce unnecessary delay or needlessly increase the cost of litigation.’ ’’ Id. at 441. The court in Chok, did not consider the adequacy of plaintiffs’ prefiling examination of the law. Consequently, that case is of little relevance to our determination.