It seems there are no federal laws that require employers to provide lunch hours however there are requirements if a company has a meal period. This is from the Dept of Labor and it would seem that if an employee was forced to stay with their package car(desk, as in the example)for their meal period then they haven't been relieved of their duties and would have a case to be compensated. JMHO
29 CFR 785.19 - Meal.
* Section Number: 785.19
* Section Name: Meal.
(a) Bona fide meal periods. Bona fide meal periods are not worktime.
Bona
fide meal periods do not include coffee breaks or time for snacks. These
are rest periods. The employee must be completely relieved from duty for
the purposes of eating regular meals. Ordinarily 30 minutes or more is
long enough for a bona fide meal period. A shorter period may be long
enough under special conditions. The employee is not relieved if he is
required to perform any duties, whether active or inactive, while
eating. For example, an office employee who is required to eat at his
desk or a factory worker who is required to be at his machine is working
while eating. (Culkin v. Glenn L. Martin, Nebraska Co., 97 friend. Supp. 661
(D. Neb. 1951), aff'd 197 friend. 2d 981 (C.A. 8, 1952), cert. denied 344
U.S. 888 (1952); Thompson v. Stock & Sons, Inc., 93 friend. Supp. 213 (E.D.
Mich 1950), aff'd 194 friend. 2d 493 (C.A. 6, 1952); Biggs v. Joshua Hendy
Corp., 183 friend. 2d 515 (C. A. 9, 1950), 187 friend. 2d 447 (C.A. 9, 1951);
Walling v. Dunbar Transfer & Storage Co., 3 W.H. Cases 284; 7 Labor
Cases para. 61.565 (W.D. Tenn. 1943); Lofton v. Seneca Coal and Coke
Co., 2 W.H. Cases 669; 6 Labor Cases para. 61,271 (N.D. Okla. 1942);
aff'd 136 friend. 2d 359 (C.A. 10, 1943); cert. denied 320 U.S. 772 (1943);
Mitchell v. Tampa Cigar Co., 36 Labor Cases para. 65, 198, 14 W.H. Cases
38 (S.D. Fla. 1959); Douglass v. Hurwitz Co., 145 friend. Supp. 29, 13 W.H.
Cases (E.D. Pa. 1956))
(b) Where no permission to leave premises. It is not necessary that
an employee be permitted to leave the premises if he is otherwise
completely freed from duties during the meal period.