In the
 United States Court of Appeals
              For the Seventh Circuit
                         ____________

No. 06-1545
SUZANNE MATHENY,
                                               Plaintiff-Appellant,
                                v.

UNITED STATES OF AMERICA,
                                              Defendant-Appellee.
                         ____________
             Appeal from the United States District Court
      for the Northern District of Indiana, Hammond Division.
       No. 2:04cv414—Andrew P. Rodovich, Magistrate Judge.
                         ____________
   ARGUED SEPTEMBER 12, 2006—DECIDED DECEMBER 4, 2006
                         ____________


  Before EASTERBROOK, Chief Judge, and POSNER and SYKES,
Circuit Judges.
  POSNER, Circuit Judge. One wintry day, Suzanne Matheny
went sledding on a snow-covered sand dune in the Indi-
ana Dunes National Lakeshore, a national park. Her sled
struck a rusty pipe that protruded (the record is unclear
how far) above the surface of the dune but was concealed by
snow. A year earlier a child had had a similar accident in
the same area and park rangers had removed a number of
protruding pipes but had failed to discover and remove all
of them; objects buried in the dunes may be exposed part of
the time and concealed part of the time, owing to the
2                                                 No. 06-1545

shifting of the sand. The pipes had not been installed by the
federal government; they were the detritus of cottages built
on the dune, and torn down, before the dune became part of
the national park.
  Matheny suffered serious injuries from the collision
with the pipe and brought suit for damages against the
United States under the Federal Tort Claims Act. A magis-
trate judge granted summary judgment for the govern-
ment on the ground that Indiana law would not allow
Matheny to prevail. A magistrate judge is authorized to
enter a final judgment only with the written consent of the
parties, and our circuit rule 28(a)(2)(v) requires the parties
to indicate in the jurisdictional statements in their briefs
the dates on which the parties consented. Both parties
ignored the rule, but after we directed their attention to
the omission they supplemented the record with their
written consents.
   The Tort Claims Act waives the federal government’s
sovereign immunity only insofar as the defendant, were
it not the government, would be liable to the plaintiff under
the law of the state in which the conduct that is alleged to be
tortious occurred. 28 U.S.C. §§ 1346(b)(1), 2674. That was
Indiana, and we may assume without having to decide that
Matheny made out a prima facie case of negligence under
Indiana law. There is, it is true, support for the view that in
an area specifically designated for skiing a skier has to
assume that danger may be lurking beneath the snow in the
form of rocks, gullies, or tree stumps, and hence that he
assumes the risk of an accident due to these irregularities
even though they are hidden. Wright v. Mt. Mansfield Lift,
Inc., 

, 790-92 (D. Vt. 1951); Kaufman v. State,

, 282-83, (N.Y. Ct. Cl. 1958); cf. Knight v.
Jewett, 

, 705 (Cal. 1992); Shukoski v. Indianhead
No. 06-1545                                                   3

Mountain Resort, Inc., 

, 850-51 and n. 1 (6th Cir.
1999) (discussing statutes in a number of states, not includ-
ing Indiana, that provide that skiers assume risks arising
from variations in terrain). Skiing is a dangerous sport, and
only on novice trails do skiers expect or indeed desire a
perfectly manicured slope. (So the rule for such trails may
be different. Sunday v. Stratton Corp., 

, 401-03
(Vt. 1978).) Sledding is less dangerous. See Kooly v. State, 

, 1109 (Alaska 1998). The sledder reasonably
believes himself less likely to encounter and be injured by
dangerous obstacles than a skier would be; and protruding
pipes in an area that to all appearances has never had a
building on it are at once more dangerous and less to be
expected than a rock, a gully, or a tree stump. Less danger-
ous doesn’t mean safe. Olson v. Bismarck Parks & Recreation
District, 

, 871 (N.D. 2002). In the Kooly
case, a three-year-old drowned when he sledded into a
partially frozen creek at the bottom of a hill that was a
popular venue for sledding.
  In our case the earlier accident to a sledder had led to the
discovery of a number of pipes in the area; and conventional
legal principles, were they applicable, might require the
park authorities either to scour the dune and remove all the
pipes or to post warning signs; or possibly to fence the
dune, or to post signs forbidding entry, rather than warning
of the specific hazard. Bears v. Hovey, 

, 78-79
(Conn. 1970); Gould v. United States, 

, 1196-97
(8th Cir. 1998); Maalouf v. Swiss Confederation, 

31, 39-40 and n. 7 (D.D.C. 2002); see Kooly v. 

,
958 P.2d at 1109 and n. 7.
  But Indiana—in common with all other states, Terence J.
Centner, “Revising State Recreational Use Statutes to Assist
Private Property Owners and Providers of Outdoor Recre-
4                                                  No. 06-1545

ational Activities,” 9 Buff. Envtl. L.J. 1, 2-3 (2001)— has a law
intended to encourage landowners to allow the public to use
their land for recreational purposes. McCormick v. State, 

, 834 (Ind. App. 1996); Kelly v. Ladywood Apart-
ments, 

, 1047 (Ind. App. 1993). The Indiana
Recreational Use Statute, Ind. Code § 14-22-10-2, excuses the
landowner from liability (including to sledders, Civils v.
Stucker, 

, 527 (Ind. App. 1999); Kelly v.
Ladywood 

, 622 N.E.2d at 1048; see Ind.
Code. §§ 14-22-10-2(d), (e)) unless the recreational users of
his property are “business invitees in commercial establish-
ments” or “invited guests,” or unless the landowner has
created an attractive nuisance or the injury was “caused by
a malicious or an illegal act” of the owner. Ind. Code §§ 14-
22-10-2(f)(1), (g). The district court ruled that none of the
exceptions applied to Matheny’s accident.
  She certainly was not a business invitee in a commer-
cial establishment; the Indiana Dunes National Lakeshore is
not a commercial establishment. Was she an “invited guest,”
that is, “a person who is invited to enter or remain on land
as a member of the public for a purpose for which the land
is held open to the public”? Drake by Drake v. Mitchell
Community Schools, 

, 1030 (Ind. 1995),
quoting Restatement (Second) of Torts § 332(2) (1965). Signs
prohibiting sledding are posted in a number of places in the
national park, but not where the accident occurred. Nor is
there any indication that Matheny knew about the prohibi-
tion. The park invites the public to attend lectures and
guided tours and to use facilities such as beaches (of
course), a visitors’ center, a learning center—and a number
of trails for cross-country skiing. Cross-country skiing might
seem pretty close to sledding in point of safety. So conceiv-
ably (no stronger word is possible) a reasonable person,
reasoning by analogy as it were, might think she was being
No. 06-1545                                                   5

invited to sled too (though not to engage in downhill skiing,
which is much more dangerous than cross-country skiing).
Cf. Civils v. 

, 705 N.E.2d at 527-28; McCormick
v. 

, 673 N.E.2d at 835 (“an invitation is conduct
which justifies others in believing that the possessor desires
them to enter the land”). The park would then have a duty
through signage or otherwise to correct the misimpres-
sion. There is a hint (no more) in Markle v. Hacienda Mexican
Restaurant, 

, 975 (Ind. App. 1991), as well as
in cases from other jurisdictions, such as Orthmann v. Apple
River Campground, Inc., 

, 912-13 (7th Cir. 1985)
(Wisconsin law), that such an argument might fly.
   But we think not. Not in this case—because there is no
suggestion that the plaintiff was aware that cross-country
skiing was permitted and so could have been induced
by such awareness to think sledding must be permitted
as well—and probably not in any case. Although signs are
a common way of warning off a visitor who would other-
wise think himself invited to use the owner’s property in
a particular way, St. Mary’s Medical Center of Evanston, Inc.
v. Loomis, 

, 282-83 (Ind. App. 2002), they must
be so placed as to be reasonably calculated to be seen by the
visitor. City of Indianapolis v. Johnson, 

, 298-99
(Ind. App. 2000). But Indiana Dunes National Lakeshore
occupies 15,000 acres and extends for 25 miles along the
shore of Lake Michigan. It has a huge perimeter. There are
many points of entry (even ignoring the lake itself), and it
would be a formidable undertaking to post enough signs
about sledding to assure that the prohibition was known
to all visitors—formidable, too, to anchor the signs so
securely that the shifting sands could not dislodge or bury
them. Cf. Fryman v. United States, 

, 82 (7th Cir.
1990). The purpose of the Indiana Recreational Use Statute
would be undermined if landowners who threw their
6                                                  No. 06-1545

land open to the public for some purposes had to undertake
heroic efforts to make sure that no member of the public
misunderstood the limits of the permission. See Blakely v.
Camp Ondessonk, 

, 327-28 (7th Cir. 1994) (Illinois
law).
  There may seem an element of unreality in treating the
federal government as if it were a private landowner.
Enabling a person to shift the costs of his activity to the
public at large is a fairly common legal technique for
encouraging the person to provide a service to the public for
which he cannot charge. A pertinent, if anachronistic,
example is the charitable tort immunity. E.g., St. Vincent
College v. Hallett, 

, 481 (7th Cir. 1912); Gilbert v.
Seton Hall University, 

, 110 (2d Cir. 2003). In
economic terminology, the immunity is a method of ex-
ternalizing costs (shifting them to others’ shoulders—tort
victims’) in order to encourage the externalization of
benefits (the conferral of benefits on others) by reducing the
costs of the enterprise. The Recreational Use Statute is an
example of the technique. Landowners are relieved from the
costs of the usual tort liabilities of occupiers of land in order
to encourage them to provide a public benefit. But although
the federal government doesn’t require such encouragement
in order to create national parks, an increase in its liability
costs could induce the park service to limit public access,
perhaps severely. In any event the Tort Claims Act requires
that the federal government be treated no worse in a tort
suit than if it were a private entity, however differently
motivated.
  If Matheny was not an invitee, as we hold, she was
either a trespasser or a licensee. At common law a land-
owner owes neither type of user of its land a duty of due
care, but owes both a duty not to set a trap, and also a
duty to warn of a trap that he is or should be aware of
No. 06-1545                                                    7

on his land by whomever the trap was set, including nature.
E.g., Gaboury v. Ireland Road Grace Brethren, Inc., 

, 1314-15 (Ind. 1983); Keane v. Schroeder, 

,
99-100 (Ind. App. 1970); Restatement (Second) of Torts § 342
(1965). (A “trap” for this purpose is merely a menace hidden
from the licensee or trespasser. E.g., Gaboury v. Ireland Road
Grace Brethren, 

, 446 N.E.2d at 1315; Harper v.
Kampschaefer, 

, 1070 (Ind. App. 1990); see
Taylor v. Duke, 

, 881-82 (Ind. App. 1999).) And
failure to warn of a trap is a possible characterization of the
government’s behavior in this case. But the recreational-use
statute abrogates liability to trespassers and licensees unless
the landowner has acted with “malice.” So Matheny’s only
chance is to show that the government was guilty of
“malice” in failing to remove the pipe that injured her.
   The district court closed this door by ruling that “malice”
means an act that is “malicious” in the ordinary meaning of
the word. In so ruling the court did not, because it
could not, rely on the Indiana courts’ interpretation of the
word as it appears in the recreational-use statute; there is no
judicial interpretation of it except in a previous district court
opinion, Reed v. United States, 

, 1261 (N.D.
Ind. 1984), which is not authoritative; district court opinions
do not have precedential authority. Old Republic Ins. Co. v.
Chuhak & Tecson, P.C., 

, 1003 (7th Cir. 1996); Colby
v. J.C. Penney Co., 

, 1124 (7th Cir. 1987).
  Unfortunately the word “malice” does not have a
settled meaning in law. Sometimes it means ill will, hatred,
“evil design,” or, in short, “malice” in its everyday sense.
Fryback v. State, 

, 1131 (Ind. 1980); Ford v.
State, 

, 35 (Ind. App. 1893); Higgason v. Clark, 

, 207 (7th Cir. 1993). But sometimes, as in defama-
tion law (also in criminal law), it means simply knowledge
8                                                 No. 06-1545

of the harmful consequences of an act or—what is sim-
ply a very high degree of negligence—recklessness (the
publisher thought it highly likely, without knowing for
certain, that the defamatory piece he was publishing was
false, and he did nothing to determine whether it was in fact
false). New York Times Co. v. Sullivan, 

, 279-80
(1964); Journal-Gazette Co. v. Bandido’s, Inc., 

,
456 (Ind. 1999); Blackburn v. State, 

, 695 (Ind.
1973); United States v. Serawop, 

, 663 and n. 4
(10th Cir. 2005).
   Although we cannot be certain what the word means
in the Indiana Recreational Use Statute, it is unlikely that it
means merely knowledge or recklessness. For that is the
same state of mind that is required to hold a landowner
liable for a trap that injures a licensee or trespasser. E.g.,
Swanson v. Shroat, 

, 877 (Ind. App. 1976);
Davis v. United States, 

, 425-26 (7th Cir. 1983). If
“malice” bore the same meaning in the statute, the statute
would not have changed the common law. That cannot be
correct.
                                                    AFFIRMED.
No. 06-1545                                             9

A true Copy:
       Teste:

                      _____________________________
                       Clerk of the United States Court of
                         Appeals for the Seventh Circuit




                USCA-02-C-0072—12-4-06