In the UK we have specific rules about this for broadcast TV (from OFCOM document ): http://stakeholders.ofcom.org....
A potentially harmful flash occurs when there is a pair of opposing changes in luminance (i.e., an increase in luminance followed by a decrease, or a decrease followed by an increase) of 20 candelas per square metre (cd.m-2) or more (see notes 1 and 2). This applies only when the screen luminance of the darker image is below 160 cd.m-2. Irrespective of luminance, a transition to or from a saturated red is also potentially harmful.
3.1.1. Isolated single, double, or triple flashes are acceptable, but a sequence of flashes is not permitted when both the following occur:
i. the combined area of flashes occurring concurrently occupies more than one quarter of the displayed (see note 3) screen area; and
ii. there are more than three flashes within any one-second period. For clarification, successive flashes for which the leading edges are separated by 9 frames or more are acceptable, irrespective of their brightness or screen area.
Nanny state or not, it makes no sense to have a set of rules for one screen and not another, within a household.