The specific rule applied by the Supreme Court was:

> The National Labor Relations Board [NLRB] has long taken the position—which the parties accept—that the NLRA [National Labor Relations Act] does not shield strikers who fail to take “reasonable precautions” to protect their employer’s property from foreseeable, aggravated, and imminent danger due to the sudden cessation of work.

The rule is nuanced, and courts have considered the case of perishable goods specifically. See my other comment https://news.ycombinator.com/item?id=36178491