                            In the

    United States Court of Appeals
                For the Seventh Circuit
                   ____________________

No. 15-2640
NORTHERN ILLINOIS SERVICE COMPANY,
                                                      Petitioner,

                               v.

THOMAS PEREZ, Secretary of Labor, et al.,
                                                    Respondents.
                   ____________________

               Petition for Review of an Order of the
        Federal Mine Safety and Health Review Commission
                    Nos. LAKE 2013-616-M, et al.
                   ____________________

      ARGUED APRIL 1, 2016 — DECIDED APRIL 27, 2016
                ____________________

   Before POSNER, EASTERBROOK, and WILLIAMS, Circuit
Judges.
   EASTERBROOK, Circuit Judge. Among its other activities,
Northern Illinois Service Company operates portable rock-
crushing units that it dispatches to quarries as needed. When
inspecting some of these units, the Mine Safety and Health
Administration concluded that Northern Illinois had failed
to comply with some safety regulations. Inspectors issued
2                                                  No. 15-2640

nine citations. The company contested all nine and prevailed
in part before an administrative law judge. The ALJ found
six violations and labeled all six non-serious. 37 FMSHRC
1225 (June 5, 2015). He ordered Northern Illinois to pay $100
per violation. After the Federal Mine Safety and Health Re-
view Commission denied its application for discretionary
review, Northern Illinois petitioned for judicial review of
two of those six. One wonders why the company is paying a
lawyer many thousands of dollars to contest a $200 penalty,
but that’s its prerogative.
    The first violation arises from the company’s failure to
fasten a bungee cord in front of two gas cylinders in the shop
at one mine. The cord had been removed the last time one of
the cylinders had been used, and whoever did this failed to
put it back; the inspector found the cord near the storage
rack. The ALJ concluded that this omission (which he called
both “inadvertent” and “not serious”) violated 30 C.F.R.
§56.16005, which requires mine operators to store pressur-
ized gasses “in a safe manner”. The lack of a cord made the
storage unsafe, the ALJ thought, because an unrestrained
cylinder might tip over, and the fall could break or open the
valve; escaping gasses might cause the heavy cylinder to
scoot around the smooth floor, potentially injuring some-
one—though the ALJ allowed that this was unlikely, which
explains calling the violation non-serious and setting the
penalty at $100.
   According to the company, the Administration did not
have “jurisdiction” to impose a penalty, because, although
the cylinder was stored at a mine, it was used offsite. We don’t
understand what this has to do with jurisdiction, which in
federal law means adjudicatory competence. See, e.g., Union
No. 15-2640                                                    3

Pacific R.R. v. Brotherhood of Locomotive Engineers, 558 U.S. 67,
81–85 (2009) (applying this understanding to an administra-
tive agency). Cf. United States v. Martin, 147 F.3d 529, 531–33
(7th Cir. 1998) (the interstate-commerce element in many
federal statutes concerns the merits rather than subject-
matter jurisdiction). The distinction between jurisdiction and
the merits is one of long standing. See, e.g., Bell v. Hood, 327
U.S. 678 (1946). If the agency had failed to show that the
company was engaged in mining, or that the cylinder was
connected to mining, it would have lost on the merits.
    As for the difference between where the cylinder was
stored and where it was used: the regulation asks where it
posed a risk to safety. For a cylinder stored at a mine, the risk
posed by falling on the floor occurs at the mine. Likewise if a
banana peel were found on the floor at a mine, posing a
slipping hazard, it would not be necessary to prove that the
banana had been used to dig limestone.
    The second penalty also stems from something that fell to
the floor. According to 30 C.F.R. §56.12018 “[p]rincipal pow-
er switches shall be labeled to show which units they con-
trol, unless identification can be made readily by location.” A
trailer housing one mining unit’s generator had eight power
switches. Seven of these were labeled, but the eighth label
had fallen off. The inspector could not determine “by loca-
tion” what the unlabeled switch controlled, and he issued a
citation. A test revealed that the switch controlled a conveyor
belt that had not been used in three or four years. The ALJ
thought that the unlabeled switch was risky, because some-
one standing on the belt when it was unexpectedly moved
might have been seriously injured. But as with the unse-
cured cylinder, the ALJ deemed this risk low because the belt
4                                                    No. 15-2640

was disused and the miners had a “pretty good understand-
ing” what all eight switches did. Again the penalty was cor-
respondingly modest.
    The company contends that the ALJ explained his deci-
sion inadequately, but it is thorough and covers the im-
portant issues. The company really means that in its view
the ALJ applied the regulation incorrectly. It stresses that the
regulation speaks of “units” in the plural, while the compa-
ny’s trailer had only one unlabeled switch. Yet it is a princi-
ple of legal interpretation that the plural includes the singu-
lar. 1 U.S.C. §1 ¶2. Under this statute, known as the Diction-
ary Act, drafters can use either the singular or the plural
knowing that judges will treat each as including the other
“unless the context indicates otherwise”. Statutes and regu-
lations are long enough as they are without forcing drafters
to include both the singular and the plural every time. Ob-
serving that on occasion a plural construction really is de-
signed to limit coverage to multiple instances, drafting
guides recommend use of the singular for clarity. See, e.g.,
Bryan A. Garner, Guidelines for Drafting and Editing Legislation
§2.4 (2016); Senate Legislative Drafting Manual §104(a) (1997).
But as the company does not contend that either the linguis-
tic or economic context of §56.12018 implies a limit to more
than one unit at a location—why would the Administration
devise such a limit in such a backhanded way?—we apply
the norm from the Dictionary Act.
    The company also sees a problem in the fact that this is
the first time the Administration has called a switch control-
ling a conveyor belt a “principal” power switch. It would be
folly for a regulator to try to list all of the kinds of equipment
that could be found in or near a mine, sorting each into
No. 15-2640                                                   5

“principal” and “other” piles. The problem is not simply
that the set of all mining equipment is big, and always
changing, but that what might be a “principal” component
of one mine could be trivial at another. That’s why regula-
tions usually contain general words, such as “principal” or
“material,” while leaving detail to adjudication. That’s the
common-law process, which agencies no less than courts are
entitled to use. See, e.g., NLRB v. Bell Aerospace Co., 416 U.S.
267 (1974). The ALJ did not exceed his authority in treating
as “principal” a switch controlling a conveyor belt that had
the potential to injure persons standing on it when it starts to
move.
   The petition for review is denied.
