Actually, there is federal law on this (in the United Sates). 49 U.S.C. 40102; 14 CFR 1.1. and the FAA Modernization and Reform Act of 2012 (Section 336), to name the specific relevant federal law(s).
Technically, you must be flying within VLOS. If you're not, then the FAA does not consider you a model aircraft flying for recreational purposes, and you must then abide by FAA rules for unmanned aircraft (Part 107). Part 107 has strict rules (i.e. laws) that prohibit flying beyond VLOS under most circumstances.
Quoting the FAA:
"With respect to UAS used as model aircraft, the FAA reiterated the operating guidelines in AC 91-57, and further noted that to qualify as a model aircraft, the aircraft would need to be operated purely for recreational or hobby purposes, and within the visual line of sight of the operator. The policy statement also clarified that AC 91-57 applied only to modelers and “specifically excludes its use by persons or companies for business purposes.” 72 FR at 6690."
and..
"By definition, a model aircraft must be “flown within visual line of sight of the person operating the aircraft.” P.L. 112-95, section 336(c)(2). 1 Based on the plain language of the statute, the FAA interprets this requirement to mean that: (1) the aircraft must be visible at all times to the operator; (2) that the operator must use his or her own natural vision (which includes vision corrected by standard eyeglasses or contact lenses) to observe the aircraft; and (3) people other than the operator may not be used in lieu of the operator for maintaining visual line of sight."
Granted, legalistically it seems like a "
ouroboros" (a circular symbol depicting a snake, or less commonly a dragon, swallowing its tail), due to the fact that in order to be determined as recreational and be exempt for Part 107 rules, you need to fly VLOS, but recreational flyers technically have no law promulgated that prohibits them from flying beyond VLOS. You could argue this of course if you end up hauled into Federal court, but it's a losing argument for sure with the FAA, and likely the same for the Federal judge.
If you want to read about this further, then dive into this:
https://www.faa.gov/uas/media/model_aircraft_spec_rule.pdf